Back before Halo development team Bungie was snapped up by Activision, it developed a title called Marathon - an open-source Doom-esque FPS which runs on Mac OS as Aleph One.
Now, developer Daniel Blezek is attempting to bring the entire Marathon trilogy to Apple's iPad.
Proposed features include HD graphics, smooth gameplay, nine unique weapons, and all levels from Marathon, Durandel, and Infinity. Infinite saved games and film recording is also set for inclusion.
Unfortunately, Blezek has hit a couple of roadblocks – most notably an audio bug - which have hindered his progress. There's also the issue of Apple's App Store terms of service, which don't allow the use of software carrying a General Public License (GPL).
When questioned about said issue by a reader of the Marathon Community Forums, Blezek replied, “There are several GPL apps on the app store, The Battle for Wesnoth being the most notable. Apple doesn't care, and the Wesnoth guys don't care so it stays, despite a possible incompatible license/terms (it's a little grey).”
Dependent on Marathon eventually making it to the App Store and the iPad version being a success, Blezek plans to port it to the iPhone as well.