Those cool guys at iD Software have released the source code to the hugely popular DOOM Classic game for iPhone & iPodTouch. It has been released under the GPL License and can be downloaded from HERE. You’ll probably also want to read the Build Instructions.
For more information check out Development on Doom Classic By John Carmack, Technical Director, Id Software.
If you’re not an iPhone developer you can purchase the game from the AppStore
Play the legendary first person shooter, DOOM, with an iPhone or iPod Touch. Fight through 36 missions in four action-packed episodes: Knee-Deep in the Dead, Shores of Hell, Inferno, and Thy Flesh Consumed.
Experience DOOM multiplayer on your mobile device, including Deathmatch and Cooperative play for up to four players via wireless internet.
Choose from three different control types and customize the interface to suit your style.
Explore the depths of Mars while utilizing the topdown map to help you explore and save your game on the fly.
Listen to the original soundtrack or disable it and use your own iPod music.