FAQ

  1. Introduction

1.1. Who actually owns and controls Qt?
1.2. What are the licensing options for Qt?

  1. Commercial Qt licensing

2.1. Is there a difference between the commercial version bought online and the perpetually licensed version bought via a sales manager?
2.2. Do you offer perpetual commercial licenses?
2.3. What is a subscription license?
2.4. Do I have to purchase a license for every developer in our team?
2.5. Can I develop with commercial Qt and install Qt creator to more than one of my computers?
2.6. Can some developers in our team working on the same project use open-source version of Qt and some developers use Commercial version of Qt?
2.7. Is it possible for some developers in our team working on the same project to use the perpetual license and some developers to use the subscription / term license?
2.8. Can I continue to use my subscription / term license without keeping my subscription active?
2.9. Can I continue to distribute my application after I have cancelled my subscription?
2.10. I have a perpetual Qt license, can I continue to use the product if I do not renew the license?
2.11. I have a perpetual license, can I continue to get new versions or updates and receive support if I do not renew the license?
2.12. I have a perpetual license; can i renew it only for some members of my team?
2.13. If I have started development of a project using the open source version (LGPL), can I later purchase a commercial version of Qt and move my code under that license?
2.14. How long is the start for free / evaluation period?
2.15. Do the Qt commercial licenses allow for easy publishing to the Apple App Store?
2.16. Which commercial Qt version grants rights to modify libraries?
2.17. Do the commercial Qt license agreements grant the right to do static linking of Qt libraries with applications?
2.18. Can I distribute Qt binaries in conjunction with my desktop / mobile application?
2.19. Do I need to have a distribution agreement to develop an embedded device with Qt?
2.20. What does a ‘joint hardware and software distribution’ mean in practice?
2.21. Does Qt commercial licensing allow for source code distribution of Qt libraries or tools?
2.22. Is there a way to add a platform to the online installer without an agreement with The Qt Company?
2.23. Under the Qt commercial licenses, can I add new functionality and distribute Qt Creator?

  1. Qt open source licensing

3.1. Why is Qt licensed also under an open source license?
3.2. Why do you have an agreement with KDE about your licensing? What KDE is and what’s the history of Qt and KDE?
3.3. Who cares about the LGPL/GPL license or LGPL/GPL license version you are using?
3.4. What is the consequence of not complying with the LGPL/GPL restrictions?
3.5. Can I use the Community open source version to develop my commercial product?
3.6. What is the difference between LGPLv2.1 and LGPLv3?
3.7. What are my obligations when using Qt under the LGPL?
3.8. Do I need to worry about LGPL when using a commercially licensed version of Qt?
3.9. I’m not sure if I’m in compliance with the licensing scheme. I am confused with the open source licensing. What should I do?
3.10. How does commercial Qt licensing work? Do all my developers need to have a valid Qt license?
3.11. Can I mix code written with Open Source Qt and commercially licensed Qt?
3.12. Is it possible to distribute applications developed with open source version of Qt via public application stores?
3.13. I have started development of a project using the open source version of Qt, can I now purchase a commercial version of Qt and move my code under that license?
3.14. Is it possible to use both LGPLv2.1 and LGPLv3 licensed libraries in the same application?
3.15. The GNU.org Compatibility Matrix suggests that I cannot combine LGPLv2.1 and LGPLv3?

  1. Online purchases and payments

4.1. When will my credit card be charged?
4.2. Can I cancel my subscription at any time?
4.3. How do I cancel my subscription?
4.4. How Do I Upgrade my Subscription from Monthly to Yearly Plan?
4.5. How long is the Start for Free period?
4.6. Can I distribute my application/s during the Start for Free period?
4.7. How do I change my billing details?
4.8. How do I change my subscription quantity?
4.9. Where can I see my current subscription status?
4.10. What credit cards are accepted?
4.11. Why can’t I make purchase even if I have an accepted card?
4.12. Which currencies are supported?
4.13. How do you manage EU VAT (Value Added Tax)?
4.14. Why does my VAT number not validate?
4.15. How is my order delivered?
4.16. Can I use support services during the start-for free period?
4.17. Is it secure to provide Credit Card details in Qt web shop?
4.18. What is PCI-DSS?
4.19. Can I get Start for Free Package without entering my Credit Card details?
4.20. Why Personal details as well as Credit Card details are required with Start for free Subscription?

1. Introduction

Qt is a commercial and open source licensed product developed by The Qt Company, together with the Qt project under the open source governance model.

In order to develop and distribute your product with Qt, you must adhere to obligations and definitions enforced by the licensing agreements.

1.1. Who actually owns and controls Qt?

Qt trademarks and most of the copyrights are fully owned and controlled by the Qt company. The development work for Qt toolkit is done through the open source governed Qt project by the Qt company r&d and external Qt contributors. The Qt project is an open ecosystem and infrastructure for developers and companies to contribute to Qt. All external contributions are licensed to the Qt company allowing re-licensing under both open source and commercial terms.

The Qt company has a binding agreement with kde free Qt foundation to ensure the availability of Qt under certain open source licenses for desktop and mobile platforms. The open source community and availability of Qt is an extremely important part of the whole value proposition of Qt and something the Qt company wants to commit to and drive forward.

1.2. What are the licensing options for Qt?

Starting from Qt 5.7, Qt is licensed under
Commercial license
LGPL3 open source license
GPL2 or GPLv3 open source license

The general Qt toolkit, consisting of Qt Essential code libraries, the Qt add-on APIs, and the Qt Creator IDE are available dual-licensed for commercial and GPL licenses. Most of the Qt APIs are available also under LGPLv3 license but not all of the Qt Add-on modules.

In addition, the commercial Qt license includes additional tools and solutions for embedded development.

2. Commercial Qt licensing

2.1. Is there a difference between the commercial version bought online and the perpetually licensed version bought via a sales manager?

The online version is offered as a term license subscription. The development license is valid only when there is an active subscription. The perpetual license is valid forever and can be renewed on an annual basis for support and updates (new releases).

2.2. Do you offer perpetual commercial licenses?

Yes. We offer a perpetual license to Qt for application development and Qt for device creation.

2.3. What is a subscription license?

With a license subscription of Qt for application development you pay a monthly fee during the time you develop with Qt. You receive all updates, and can use support, as well as the online systems. After the subscription ends, you cannot develop with Qt any more, but the applications you created can be used

2.4. Do I have to purchase a license for every developer in our team?

Yes. Each developer must have their own assigned Qt license. It’s not permitted to mix Qt commercial licenses with Qt LGPL licenses in one project.

2.5. Can I develop with commercial Qt and install Qt creator to more than one of my computers?

Yes. You can install Qt and our development tools to as many computers as needed as long everyone using Qt has a valid commercial license. Our licenses are per individual, so all members of your project team using Qt need to have a license.

2.6. Can some developers in our team working on the same project use open-source version of Qt and some developers use Commercial version of Qt?

No. Each developer must have their own assigned Qt license. Mixing Qt commercial licenses with Qt open-source licenses in one project/product is not permitted.

2.7. Is it possible for some developers in our team working on the same project to use the perpetual license and some developers to use the subscription / term license?

Yes. It is allowed to use both perpetual and term licensed Qt in the same team. Note that it is not permitted in the same project to have some developers using perpetual and/or term licenses together with the open-source version of Qt.

2.8. Can I continue to use my subscription / term license without keeping my subscription active?

No. It is not permitted to continue development if your subscription is not active. The rights to continue using the tools expire when the subscription is cancelled.

2.9. Can I continue to distribute my application after I have cancelled my subscription?

No, you need to have a valid license to distribute your application. All applications that have been distributed during the subscription period are valid as such, so your users can continue using them as usual.

2.10. I have a perpetual Qt license, can I continue to use the product if I do not renew the license

Yes. You can continue to develop with the version you have but you won’t receive any updates nor have access to Qt support.

2.11. I have a perpetual license, can I continue to get new versions or updates and receive support if I do not renew the license?

No. You must have an active perpetual license in order to get new versions/updates and receive support from The Qt Company.

2.12 I have a perpetual license; can i renew it only for some members of my team?

No. The whole team has to have active development licenses in order to use support and to receive updates.

2.13. If I have started development of a project using the open source version (LGPL), can I later purchase a commercial version of Qt and move my code under that license?

This is not permitted without written consent from The Qt Company. If you have already started the development with an open-source version of Qt, please contact The Qt Company to resolve the issue. If you are unsure of which license or version to use when you start development, we recommend you contact The Qt Company to advise you on the best choice based on your development needs.

2.14. How long is the start for free / evaluation period?

The commercial evaluation term period is thirty (30) days. During that time, you can develop with Qt, but you are not allowed to distribute your applications before you purchase a paid license. After the free 30-day period, you need to either purchase a license or cease from using the free trial.

2.15. Do the Qt commercial licenses allow for easy publishing to the Apple App Store?

Yes. The Qt commercial licenses allow publishing to the Apple AppStore or other stores (including those that require static linking).

2.16. Which commercial Qt version grants rights to modify libraries?

All commercially licensed Qt versions allow modification of libraries for application development. If you need technical support related to source code builds of Qt, at the minimum, Silver support offered by The Qt Company is needed.

2.17. Do the commercial Qt license agreements grant the right to do static linking of Qt libraries with applications?

Yes.

2.18. Can I distribute Qt binaries in conjunction with my desktop / mobile application?

Yes. Distribution of Qt libraries in binary form in conjunction with the developed application is allowed under the Qt for Application Development license agreements. A separate agreement is not needed. The platforms for which you have the right to distribute are listed in your license certificate (in your Qt Account).

2.19. Do I need to have a distribution agreement to develop an embedded device with Qt?

Yes. A distribution agreement explaining the terms for distributing the Qt libraries is included in your Qt license agreement. When you create an embedded device you typically have ‘joint hardware and software distribution’, which is subject to a distribution fee, please contact us for more information.

2.20. What does a ‘joint hardware and software distribution’ mean in practice?

If you are making an embedded device with Qt, you most likely will have ‘joint hardware and software distribution’ as described in the Qt for Device Creation license agreement. This is subject to a distribution fee, please contact us for more information.

2.21. Does Qt commercial licensing allow for source code distribution of Qt libraries or tools?

No, it does not. Qt libraries may be distributed in binary form only with the application.

2.22. Is there a way to add a platform to the online installer without an agreement with The Qt Company?

No. You must contact us. We are happy to add more platforms to the online installer.

2.23. Under the Qt commercial licenses, can I add new functionality and distribute Qt Creator?

No. Distribution of Qt Creator is prohibited without a separate agreement with The Qt Company.

 

3. Qt open source licensing

3.1. Why is Qt licensed also under an open source license?

We believe in the Free Software movement where using software comes with certain rights, but also certain obligations. Use of open source licensing gives users four primary degrees of freedom when using Qt applications or devices:

  • The freedom to run the program for any purpose
  • he freedom to study how the program works and adapt it to specific needs
  • The freedom to redistribute copies so you can help your neighbor
  • The freedom to improve the program and release your improvements to the public, so that the whole community benefits

The Free Software community has thrived because of these rules, but there are also developers who never intend to observe these rules, and thus should get a commercial license. The Qt Company exists to support both sets with the dual offering.

3.2. Why do you have an agreement with KDE about your licensing? What KDE is and what’s the history of Qt and KDE?

KDE is an international free software community, founded in 1996, producing an integrated set of cross-platform applications for desktop and mainly known for its Plasma Desktop environment, which is provided as the default work environment on many Linux distributions. KDE software is based on the Qt framework. In the early days of Qt, the KDE project and community was the biggest driving force in building the developer ecosystem around Qt.

In the very early days, Qt was already dual-licensed, but the source code was available under proprietary open source licenses. Compromises with KDE were sought to ensure that Qt would be available for their use under appropriate open source licensing even if Trolltech (the company that founded Qt) would be bought or go bankrupt. As a result, The KDE Free Qt Foundation was founded.

The KDE Free Qt Foundation is an organization with the purpose of securing the availability of the Qt toolkit for the development of Free Software and in particular for the development of KDE software. The Foundation was originally founded by Trolltech and the KDE e.V. (the legal non-profit organization behind KDE) in 1998 and it has a license agreement that ensures the availability of Qt under LGPLv3 and GPLv3 licenses for major desktop and mobile platforms. The license agreement has been updated couple of times over the years, mainly because of acquisitions around Qt or updates to licenses and platforms.

3.3. Who cares about the LGPL/GPL license or LGPL/GPL license version you are using?

You, unless you are using Qt under a commercial license. Your customers and end users care! LGPL & GPL are copyleft licenses, which means that the license follows with your product to your end users and customers.

3.4. What is the consequence of not complying with the LGPL/GPL restrictions?

If software using these open source licensed libraries does not fully comply with the license obligations you will lose your license and related distribution rights.

3.5. Can I use the Community open source version to develop my commercial product?

It depends on how you license and distribute your product. The open source version of Qt is mainly distributed under the LGPL, version 3 and GPLv2/v3. You will need to fulfill the license obligations for these licenses when using Qt in your product.

3.6. What is the difference between LGPLv2.1 and LGPLv3?

LGPLv3 is the current version of the GNU Lesser General Public License. LGPLv2.1 is an older version and not recommended by the Free Software Foundation for new projects anymore. Both licenses have the same intention, namely to protect the freedom of users to use and modify the software licensed under LGPL.

LGPLv3 makes this intention very explicit. You have to provide means to the end user to install a modified version of the library licensed under LGPLv3 and run your software using that modified library. In practice, this for example refers to:

  • Tivoization – Explicitly not allowing creation of closed devices where the end user does not have the LGPL granted rights for the Qt open source libraries
  • DRM and hardware encryption – This cannot be used to circumvent these obligations
  • Software patent retaliation – Where all users of the software are granted licenses thus making software patent retaliation of any potentially patented software in the distributed software meaningless.

3.7. What are my obligations when using Qt under the LGPL?

If you are using Qt under the LGPLv3, there are a couple of obligations you will need to fulfill :

  • Firstly, you have to note that some Qt open source modules are not available for LGPLv3 license, for example Qt Charts, Qt Data Visualization and Qt Virtual Keyboard. These modules are only available under GPLv3 for open source usage.
  • You will need to deliver the complete source code of Qt (including all modifications you did or applied) to your users/customers. Alternatively you need to provide a written offer with instructions on how to get the source code. Please also note that this has to be under your control, so a link to the source code provided by the Qt Project or Qt Company is not sufficient.
  • The LGPL allows you to keep the source code of your application private as long as it is “work that uses” the library. Dynamic linking is usually recommended here.
  • The user of your application has to be able to re-link your application against a different or modified version of the Qt library. With LGPLv3 it is also explicitly stated that the user needs to be able to run the re-linked binary on it’s intended target device. It is your obligation to provide the user with all necessary tools to enable this process. For embedded devices, this includes making the full toolchain used to compile the library available to users. For parts licensed under LGPLv3 you are obliged to provide full instructions on how to install the modified library on the target device (this is not clearly stated with LGPLv2.1, although running the application against the modified version of the library clearly is the stated intention of the license).
  • The user of an application or device using LGPL licensed software has to be notified of their rights by providing a copy of the LGPL license to the end user and displaying a prominent notice about your usage of LGPL licensed software.

The above freedoms cannot in any way be restricted by other licensing terms. If an application is not fully following all the obligations as outlined above, it is not allowed to be distributed at all.

You will also need to make sure that you are not using any GPL licensed modules.

3.8. Do I need to worry about LGPL when using a commercially licensed version of Qt?

Usually, not. When using the commercially licensed version of Qt, we provide almost all of Qt under a commercial license terms.

A few modules in Qt, however, use code from the WebKit project licensed under LGPLv2.1. These modules are Qt Script, Qt WebKit and Qt WebEngine. So when using these modules, you will need to fulfill the license obligations of LGPLv2.1 (but not LGPLv3).

Please also note that you can avoid using Qt Script, as the Qt Qml module contains a fully functional JavaScript engine that can be used instead. This module is available under commercial licensing terms and doesn’t introduce a dependency to LGPL licensed code.

As a commercial license user, in practice, you only need to consider license obligations of LGPLv2.1, and only if you make use of Qt WebEngine or Qt WebKit .

3.9. I’m not sure if I’m in compliance with the licensing scheme. I am confused with the open source licensing. What should I do?

It is always recommended to contact a lawyer familiar with open source licenses for a full review of your project to determine whether you can fulfill all of the obligations of applicable open source licenses (LGPLv3/GPLv2/GPLv3). You can have a high level view of your options with the “Get Started with Qt” guide in our Qt.io/download –page. In case there is any doubt on whether the requirements of the open source licenses can be met in full, the commercial licensing option of Qt is often the best choice to avoid legal setbacks. We’re also happy to talk to you about your situation, but we aren’t in the position to provide any legal guidance.

3.10. How does commercial Qt licensing work? Do all my developers need to have a valid Qt license?

Qt is licensed per named developer, so all developers working with Qt libraries or tools should have a license of their own, which also gives them direct access to Qt Support.

If you are building and distributing applications for desktop or mobile platforms you should acquire a license for “Qt for Application Development”. This can be purchased directly from Qt Sales or through the online webshop via http://Qt.io through a monthly subscription model.

If you are building and distributing devices you should acquire a license for “Qt for Device Creation”. This license can be purchased through Qt Sales. In this case, you will also need a separate distribution license for your devices.

Both of the commercially licensed products may be evaluated free for 30 days through http://www.Qt.io under the commercial license, so that you can already start working with the proper commercial license.

3.11. Can I mix code written with Open Source Qt and commercially licensed Qt?

Your whole development team should be using the same license and they should be using it during the whole development lifecycle. Therefore, if you plan to use a commercial Qt license, you should have it in place at the beginning of your project work.

 

If you want to migrate from open source Qt to a commercial license, you should contact us directly to discuss about your options in practice.

3.12. Is it possible to distribute applications developed with open source version of Qt via public application stores?

Each application store has their own unique terms and conditions, which may or may not be compatible with distributing applications under LGPL or GPL licenses. Based on the current terms and conditions (2015) of some of the widely used application stores it should be feasible to fulfill LGPL and GPL requirements with Google Play store and Microsoft Windows store. Distribution via Apple AppStore is more challenging as the terms and conditions of the store are more restrictive regarding the freedoms provided by LGPL and GPL open source licenses. The commercial license of Qt is compatible with the terms and conditions of all the leading application stores and thus typically the best choice for distributing a closed source application in various application stores.

3.13. I have started development of a project using the open source version of Qt, can I now purchase a commercial version of Qt and move my code under that license?

Yes. Projects distributed under the commercial version of Qt must also be developed under the commercial version of Qt. If you have already started the development with an open-source version of Qt we will work together to find a solution to move your code base over to commercial licensing. If you are unsure of which license or version to use when you start development, we recommend you contact The Qt Company to advise you on the best choice based on your development needs.

3.14. Is it possible to use both LGPLv2.1 and LGPLv3 licensed libraries in the same application?

Yes, it is possible to use both LGPLv2.1 and LGPLv3 licensed libraries in the same application for example by having these as separate shared libraries. Doing this does not require changing license in either of the libraries, and it is possible to select a proprietary license for the application, if desired.

3.15. The GNU.org Compatibility Matrix suggests that I cannot combine LGPLv2.1 and LGPLv3?

If LGPLv2.1 code and LGPLv3 code are in different shared libraries, then they can be used in the same application, and you can license your application with a proprietary license / LGPLv2.1 / LGPLv3 as you wish.

4. Online purchases and payments

4.1. When will my credit card be charged?

Your credit card will be charged at purchase or after Start for Free period.

4.2. Can I cancel my subscription at any time?

You can cancel your subscription any time. However, note that when you cancel your subscription you will not be able to access Qt Creator and continue developing. Our tools are only available with an active subscription.

4.3. How do I cancel my subscription?

You can cancel your subscription from Qt Account Portal payments page.

4.4. How Do I Upgrade my Subscription from Monthly to Yearly Plan?

You can Upgrade Your plan as a self service via Qt Account Portal. Or contact us, and we’ll assist you.

4.5. How long is the Start for Free period?

The commercial evaluation term period is thirty (30) days. During that time, you can develop with Qt, but you are not allowed to distribute your applications before you purchase a paid license. After the free 30-day period, you need to either purchase a license or cease from using the free trial.

4.6. Can I distribute my application/s during the Start for Free period?

The commercial evaluation term period is thirty (30) days. During that time, you can develop with Qt, but you are not allowed to distribute your applications before you purchase a paid license. After the free 30-day period, you need to either purchase a license or cease from using the free trial.

4.7. How do I change my billing details?

You can change your billing details, for example credit card number, from Qt Account Portal payments page.

4.8. How do I change my subscription quantity?

You can modify your subscription from Qt Account Portal payments page.

4.9. Where can I see my current subscription status?

Please log in to your Qt Account.

4.10. What credit cards are accepted?

We accept Visa, MasterCard and American Express.

4.11. Why can’t I make purchase even if I have an accepted card?

It may be that the card issuer does not allow recurring payments or that internet payments are disabled. Please contact us if you have any problems with your payments.

4.12. Which currencies are supported?

USD.

4.13. How do you manage EU VAT (Value Added Tax)?

Companies in the EU will pay 0% if they provide a valid company VAT number that can be validated during the purchase process. In Finland ,companies pay 24% VAT, but they can claim the 24% tax fee via Finnish tax officials. Otherwise buyers must pay 24% VAT due to EU taxation. After purchasing, customers will receive a receipt to be presented to the tax authorities. Please note that the VAT number must be entered without spaces or punctuation and with country code.

Customers in non-EU countries don’t have to pay VAT.

4.14. Why does my VAT number not validate?

The EU-provided interface may be unreachable and therefore the VAT number cannot be validated.

The data in EU provided information may be incorrect and your number is not there or is incorrect. In this case it might be a good idea to contact your local tax authority.

You can claim the 24% tax fee via your own tax officials.

4.15. How is my order delivered?

Once your purchase is complete, you will receive a welcome email with information about your Qt Account. You can begin your download via the Qt Account where you will also be able to get updates and log support cases.

4.16. Can I use support services during the start-for free period?

Qt Support services are available via Qt Account Portal.

4.17. Is it secure to provide Credit Card details in Qt web shop?

Our payment system is PCI-DSS Level 1 compliant, and is recognized on the Visa Global Registry of Service Providers. We meet or exceed all industry-standard payment security practices to protect you and your customers.

4.18. What is PCI-DSS?

The Payment Card Industry Data Security Standard (PCI-DSS) provides a framework for developing a robust security process for credit card transactions. Any merchant or merchant service provider accepting, transmitting, and/or storing cardholder data must be PCI compliant.

4.19. Can I get Start for Free Package without entering my Credit Card details?

You can contact to Qt Sales via “Contact us” link

4.20. Why Personal details as well as Credit Card details are required with Start for free Subscription?

We are constanly looking at our product portfolio, and best possible options to serve our customers better. As a customer orientated company, your feedback would be very much appreciated.