PythonQt is distributed under the LGPL license, so it pairs well with the LGPL of the Qt 4.5 release and allows to be used in commercial applications when following the LGPL 2.1 obligations.
The build system of PythonQt makes use of a modified version of the LGPL'ed QtScript generator, located in the "generator" directory.
See http://qt.gitorious.org/qt-labs/qtscriptgenerator for details on the original project. Thanks a lot to the QtJambi guys and the QtScript Generator project for the C++ parser and Qt typesystem files!
The PythonQt wrappers generated by the generator located in the "generated_cpp" directory are free to be used without any licensing restrictions.
The generated wrappers are pre-generated and checked-in for Qt 4.8, so you only need to build and run the generator when you want to build additional wrappers or you want to upgrade/downgrade to another Qt version. You may use the generator to generate C++ bindings for your own C++ classes (e.g., to make them inheritable in Python), but this is currently not documented and involves creating your own typesystem files (although the Qt Jambi examples might help you).