FPS gaming pioneer John Carmack announced that the Doom 3 id Tech 4 engine is set for an open source release.
"Doom 3 source is packaged and tested, we are waiting on final lawyer clearance for release," Carmack tweeted.
The release of the game engine continues a tradition of the company providing older game engines free of charge. Last year the id released source code for Wolfenstein: Enemy Territory and Return To Castle Wolfenstein.
As with previous engines such as the Quake 3 engine, indie game developers are expected to put the code to good use in their own creations.
When Carmack originally announced the release at QuakeCon earlier in the year he challenged other game developers to release their code, arguing that it helps the community of pro and amateur game developers.