QGroundControl (QGC) is dual-licensed as Apache 2.0 and GPLv3. All contributions have to be made under both licenses. Users of the codebase are free to use it under either license.
QGroundControl licensing rules out the re-use of any copyleft (e.g. GPL) licensed code. All contributions must be original or from a compatible license (BSD 2/3 clause, MIT, Apache 2.0).
The dual approach is necessary to be able to offer QGroundControl through the iOS and Android app stores and offers the open source community choice.
The Apache 2.0 License is a permissive license which allows QGC to be built and used in any environment, including proprietary applications. It allows QGC to be built for mobile app stores. When building with Apache 2.0 a commercial Qt license is required.
The GPL v3 License is a strong copyleft license. When building QGC under this license the open source version of Qt can be used. Our licensing grants the permission to use a later version of the license, however, contributions have to be made under 3.0.
The QGroundControl documentation, artwork and images are licensed under CC BY 4.0.