GtkRadiant's roots lie in id Software's in-house tools. Some of the early UI design decisions influencing it could be seen in QuakeEd, the original Quake mapping tool for NextStep. The first direct code ancestor however was QE4, the in house Quake II level editor id Software used to build Quake II levels and later made available with the Quake 2 SDK. Robert Duffy used the released QE4 source code to develop QERadiant which became a very popular editor. id Software took the code in-house again to develop Q3Radiant, the Quake III Arena level design tool. All these tools were Windows-only applications.
GtkRadiant was released in 2001 as a modification of Q3Radiant introducing two major changes: It used the GTK+ toolkit so that it could also support Linux and Mac OS X, and it was also game engine-independent, with functionality for new games added as game packs.
GtkRadiant is free software distributed under GNU General Public License. For a long time, the application source code was publicly available from id Software's Subversion repository, and it was in a dual license where new code was under GPL-compatible free software licenses and the core Q3Radiant code was under id Software's proprietary license, primarily because it used parts of Quake III Arena code. This dual-license system made development difficult, and inhibited use of the editor in commercial projects. On August 19, 2005, Quake III Arena source code was released along with the Q3Radiant source code. The license for both the GtkRadiant editor and toolset (notably Q3Map2, the BSP compiler) was changed in February 2006, and publicly released under the GPL on February 17.
There is one prominent fork, DarkRadiant, which is specifically optimised for id Tech 4 engine. It was originally created for the needs of Doom 3 mod called The Dark Mod. DarkRadiant holds many improvements over GTKRadiant.
ZeroRadiant (or GTKRadiant 1.6.0) is an upcoming version of the GTKRadiant level editor based upon the 1.4.0 architecture and design. It is currently in development for new id Games projects. It will be used to create maps for a number of computer games. It is maintained by id Software together with a number of volunteers.
Support has previously existed for the following:
In addition, the following games and projects use GtkRadiant as a map editor, by using the GtkRadiant Quake III Arena game pack and an external map compiler or converter:
Custom game packs exist for these games: