John Carmack has released the source code to the legendary first-person shooter Doom 3. The code can be downloaded via the Github.com Web site.

Carmack made some changes to the source code to comply with license restrictions – most notably, the removal of code used for shading commonly referred to as “Carmack’s Reverse.” The technique was the focus of a patent dispute between Id Software, Carmack’s company, and Creative Labs, which patented the process in 1999.

Also, the actual game data has been removed, of course, so you can’t just compile the code and get a working game. But the Doom 3 source is of immense interest to game developers interested in seeing what makes the game tick – and perhaps incorporating some of that code into their own products.