The Qt toolkit.
Several bits of Qt and Qt Creator code are copied into GammaRay: ModelTest, ResourceModel, Qt Designer type icons, QPaintBuffer.
The sources can be found in GammaRay/3rdparty/qt.
Project Homepage, upstream version: 4.8 - 5.10
Copyright (C) 2015 The Qt Company Ltd.
GPLv3, LGPLv3, commercial.