Qt now exists in a number of flavours, for various platforms, and these are licensed under various licences.
These are:
Qt/X11 - Qt for Unix X Window System - GPL
Qt/Mac - Qt for Apple Mac OS X - Proprietary
Qt/Windows - Qt for Microsoft Windows - Proprietary (obsolete version free)
Qt/Embedded (designed for PDAs) - GPL
This gave rise to two efforts. First, the Harmony toolkit which sought to duplicate the Qt Toolkit under a free software license. Secondly, the GNOME desktop that was meant to supplant KDE entirely. The GNOME Desktop used the Gtk+ toolkit which was written for the GIMP, and uses mainly the C programming language. Gtk+ attempts to be cross-platform just like Qt.
Compromises were sought between KDE and Troll Tech wherein Qt would not be able to fall under a more restrictive license than the QPL, even if Troll Tech was bought out or went bankrupt. This did not satisfy all the critics, and finally, on September 4, 2000, Troll Tech announced that the upcoming Qt 2.2 release will be licensed under the GPL. Qt 2.2 was released on September 6, 2000, KDE 2.0 followed on October 23, 2000.
Troll tech has subsequently released Qt 3 under the GPL and there is a corresponding KDE 3.x release series.
wikipedia.org dumped 2003-03-17 with terodump