1. Introduction to Qt
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.