https://www.theregister.co.uk/2020/01/28/new_qt_terms_changes_are_necessary_for_our_business_model/

The Qt Group is making changes to the terms under which its popular open-source Qt library is available to encourage more commercial licensees and a higher level of contribution from users.

Qt is a cross-platform C++ framework with official bindings for Python as well as community support for many other languages. It is suitable for embedded, mobile and desktop applications, and the company provides design tools (with support for the QML language for defining a user interface) and an IDE that runs on Windows, Linux and macOS.