Rage developer id Software has released the source code for its first person shooter, Doom 3.

Developers and interested parties can now download the code completely free, id co-founder John Carmack confirmed on Twitter last night.

Doom 3's inner workings were ready to go at the start of the month, but last-minute legal issues temporarily held up its release - Carmack was forced to re-write some of the code to placate "skittish" lawyers nervous about the release of a particular section.

The release was announced by Carmack during his keynote speech at this year's Quakecon event, where he expressed the wish for other developers to follow suit.

The full code is available to download from Github.