After some last-minute rewriting prompted by legal concerns, id Software has finally released the source code to Doom 3. id Technical Director John Carmack updated his Twitter feed yesterday afternoon with the following:
https://github.com/TTimo/doom3.gpl Timothee Besset did most of the work of getting it ready for release – thanks!
The Github link in Carmack's tweet points to the entire source code release, which is provided under the GNU General Public License v3.0 along with build instructions. As those instructions point out, though, Doom 3's game assets are still copyrighted and aren't included with the source code. Folks will have to provide their own maps, models, and textures—or just dig up their old copy of Doom 3 and grab the assets from that, if they don't intend to distribute them.
Carmack also tweeted that, instead of the contentious "Carmack's reverse" shading algorithm (a.k.a. depth fail, which is patented by Creative Labs), he used the "preload" technique described here "where it can't be shown the player is outside a shadow volume."