I'm not sure if the source was available before. But if so, I'm wondering if anyone has compared it to the original source to see what was changed? Anything interesting? Anything major?
John Carmack took a few months break from Rage development to work on these (at least on Wolfenstein, not sure about Doom) [1], so there will definitely be substantial differences to adapt to iOS, like - I'm guessing - OpenGL-ES code and touch controls.
here's a write-up from Carmack about his Wolfenstein iPhone development adventures: http://www.idsoftware.com/wolfenstein3dclassic/wolfdevelopme...
Everyone benefits from Open Source, even the original creators.