[wjoe]

PyQt5 is GPL licensed. Not expensive, but perhaps not suitable for your closed source project. There is also a commercial license available, probably that is expensive.

PySide2 is LGPL licensed, so more likely to be suitable for you, since it can be used without having to provide the source of your application.

Both libraries serve the same purpose of providing Qt5 bindings for Python in slightly different ways. PySide2 has become officially supported by Qt recently, and has generally been the preferred option for closed source development due to the licensing.