GtkRadiant is a level design program developed by id Software and Loki Software. It is used to create maps for a number of computer games. It is maintained by id Software together with a number of volunteers.

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.

Game packs exist for the following games. Generally, this includes support for all expansions and modifications as well.

*Doom 3
*Quake
*Quake II
*Quake III Arena
*Quake 4
*Return To Castle Wolfenstein
*Wolfenstein: Enemy Territory
*Half-Life
*Heretic II
*Soldier of Fortune II: Double Helix
*Star Trek: Voyager Elite Force
*Star Wars Jedi Knight II: Jedi Outcast
*Star Wars Jedi Knight: Jedi Academy
*Medal of Honor: Allied Assault
*Call of Duty
*Nexuiz
*Tremulous

KatsBits notes an update to the new Radiant site, which announces a major release to GtkRadiant. Some of the new and improved features include added game support and Vista compatibility, have a look:

• Enhanced Texturebrowser, makes browsing your textures alot easier
• Texturetagging, create custom categories for your textures to get a better workflow
• Brushexport Plugin, export selected Brushes as Wavefront files and load them into your 3D application
• Lighting previewmode for Doom3, Quake 4 etc (Press F3).
• Improved camera strafing (Ctrl), press (Ctrl + shift) to strafe forward
• Adjustable strafespeed (Shift with KeyPad+, KeyPad-)
• Select inside/touching now work with multiple selectionbrushes allowing complex selectionshapes
• Vista compatibility
• UI improvements
• Sunplug (Mapcoordinator-plugin for ET)
• Support for many more games: Doom3, Quake 4, Prey, Warzow, Nexuiz etc
• Maya-style tools for translate (w) and rotate (r):
• Axis-constrained translate/rotate in 2d and 3d views
• Outliner (aka entity lister), shows an editable tree-view of the current scene
• Faster rendering using frustum culling
• Very fast undo, even with large changes.
• Complete update of all libraries
• Tons of bugfixes and more

Read more and download the latest GtkRadiant here.