Before proceeding to download Qt for open source development make sure you are choosing the right license for your project.
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.
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 .
Check out which components are available under the different open source models in the Qt Product Map.
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:
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.
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.
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.