"The PySide project provides LGPL-licensed Python bindings for the Qt cross-platform application and UI framework. PySide Qt bindings allow both free open source and proprietary software development and ultimately aim to support all of the platforms as Qt itself." Previously, the PyQt bindings were not licensed LGPL. If one wished to make a commercial application, then one previously had to purchase a commercial license for PyQt. Now it is possible to dynamically link to the LGPL-licensed PySide bindings instead. The PySide bindings are API compatible with PyQt.