id Software's John Carmack has revealed that the planned release of Doom 3's source code has been put on hold over concerns of patent infringement, forcing the legendary programmer to rewrite portions of the 2004 game.
As Carmack announced on Twitter earlier this week, ""[id's] Lawyers are still skittish about the patent issue around 'Carmack's reverse.'" Though it sounds like an advance wrestling technique, Carmack's Reverse is actually a shadow-stencilling algorithm that the id-cofounder discovered while he was working on Doom 3. He wasn't the first to invent the technique, though, and id later found out that the algorithm had already been patented by Creative Labs.
The two companies reached an agreement that allowed Doom 3 to release with the algorithm intact (and with no money changing hands), but id's lawyers are evidently worried that open-sourcing the patented code along with the rest of the game could have serious legal ramifications.
Now it looks like Carmack will have to code an entirely different technique to achieve the same results. While that shouldn't be too difficult — both graphical techniques and computer hardware have made significant advances in the last seven years — it does push the open source release back even further.