id Software will release the source code for Doom 3 later this year.
Speaking at Quakecon 2011, id's technical director John Carmack revealed that parent company Zenimax was supportive of the move. He also challenged other developers to release their own source code, arguing that it helps the community.
The source code will be available after the launch of Rage, which hits shelves in October.
id's engine Id Tech Five will also go open source, but not until it's no longer used for official projects. Carmack speculated that this could be as long as ten years away.
Carmack refused to talk about id's next big project, Doom 4, but did reveal that there were already plans for Rage 2. He also described a browser-version of classic title Wolfenstein as off the table.
Quakecon is an annual gaming event held in Dallas, Texas, and and curated by id Software. The event will run until August 7.