The Doom 3 source code has been released and is available now on Github . According to John Carmack's Twitter feed , the source code was delayed when lawyers had a bit of a wobble over some patent problems. With the addition of a few lines of code and the tweaking of a few more, the release was good to go . Releasing source code is a bit of a risky move, and takes time and money to do, so it's heartening to see id dishing out the data for free. Indie devs and code enthusiasts, go forth and conquer!