• PyQt is a set of Python v2 and v3 bindings for The Qt Company's Qt application framework and runs on all platforms supported by Qt including Windows, OS X, Linux, iOS and Android. PyQt5 supports Qt v5.
• https://riverbankcomputing.com/software/pyqt/intro
• PyQt is needed by Qgis to load python extensions (From https://github.com/qgis/QGIS/blob/master/INSTALL : for python support - SIP >= 4.12, PyQt >= 5.3 must match Qt version, Qscintilla2)
• Dual licensed on all supported platforms under the GNU GPL v3 and the Riverbank Commercial License.
• PyQt5_gpl-5.8.2.tar.gz

I don't think a lot of users needs this (I do ;)) but it was already asked before : T3397