Open Source Qt Use

Before proceeding to download Qt for open source development make sure you are choosing the right license for your project.

Considerations
Your obligations
Virtuous Cycle
Due diligence
Qt source code
Start contributing

What to Consider

The Qt framework is available under both open source and commercial licenses. This dual-licensing model is based on the principal of quid pro quo – roughly meaning “something for something.”

Simply put, this is how it works: In return for the value you receive from using Qt to create your application, you are expected to give back by contributing to Qt or buying Qt.

Contribution via Open Source

When selecting an open source license for your project, you contribute to free and open source software development by using Qt under any of the following licenses: LGPL version 3, GPL version 2 and GPL version 3.

Basic Premises of the Qt Open Source Model

GPL – All users have the rights to obtain, modify and redistribute the full source code of your application. Your users are granted rights founded on the four freedoms of the GNU General Public License.

LGPL – Any modification to a Qt component covered by the GNU Lesser General Public License must be contributed back to the community. This is the primary open source Qt license, which covers the majority of Qt modules.

_{Please note that there are parts of Qt that are only provided under GPL for open source users that will require you to license your application under a GPL compatible license. Qt also ships with third party open source components that might require respective licensing compliancy, if used. See details of other licenses inside Qt .}

icon_resources_infographic Check out which components are available under the different open source models in the Qt Product Map.

Open Source Usage Obligations

The majority of the Qt modules are available under the LGPL v3 and GPL v3 open source license. When developing under this license your obligations are to:

Provide a re-linking mechanism for Qt libraries
Provide a license copy & explicitly acknowledge Qt use
Make a Qt source code copy available for customers
Accept that Qt source code modifications are non-proprietary
Make “open” consumer devices
Accept Digital Rights Management terms, please see the GPL FAQ
Take special consideration when attempting to enforce software patents FAQ

If the open source license model isn't the right fit for your project or you have concerns about being able to comply to the license terms, contact us. We can help you secure rights to develop, use and distribute your application under a choice of commercial license packages.

Please note that it's not allowed to use both open source and commercial licensing in the same application or device. Visit the Qt licensing FAQ to learn more

Your Contributions Matter

Since our funding comes from selling commercial licenses and services, it is essential that we reach commercial readiness as quickly as possible. This can only be achieved through active community participation in our development process. The Qt community plays a vital role in ensuring the stability, richness and quality of Qt. With Qt releases being thoroughly tested by thousands of open source developers around the world, we get the boost needed to support the cost of driving further development of Qt. It ensures the future of Qt. We call this our Virtuous Cycle.

Qt has an online marketplace, featuring (primarily free) Qt extensions, including those produced by the KDE community. To learn more about what can be accessed, and even to host your own content, visit the Qt Marketplace.

Get Started

Due Diligence

Confirm that you can abide by the obligations of Qt open source licensing.

When deciding which license to use, please check your corporate open source policy or consult a software licensing legal expert.

Find more information on Qt licensing and open source obligations here.

Source Code

Set up your local development environment, get the Qt source code from the repositories, and build the libraries on your machine.

Grab the code at https://code.qt.io/ or if you need help, the community not only contributes to Qt, but also to the Qt Wiki where you can learn how to get started.

Start Contributing

Qt source code repositories are open to the public, which means that you can immediately help guide and shape the future development of Qt by contributing code, translations, examples and more.

Learn what's involved when contributing to the Qt project here.

Looking for Qt binaries?

Find them in the Qt Online Installer. It will steer you to the right download version and help you install tools and add-on components that are available for your open source license.