GtkRadiant is the official level design toolchain for games powered by id Tech engines from id Software, and is maintained by a community of volunteers. GtkRadiant is powered by the GTK+ Project and released under a GPL license.
The official GtkRadiant website has moved to a new home at Icculus. The source code and issue tracker is now on GitHub. RobotRenegade will continue to host download mirrors of GtkRadiant files for your convenience. It's all part of what we're doing to build better level design tools so you can build better games.