Actually, from what I can tell the source *is* the Duke3D source, in order to have the entire game all you need is the game data files.
It doesn't look *too* complex (famous last words :-D ), seems like the really tricky thing will be porting the assembler functions to either C or PPC assembler. My knowledge of x86 assembler is reasonable, but PPC assembler is closer to zip :-) ). Still, if I'm going to burn some time this will be more direct than trying to speed up Bochs...
So, when are your pals at Hyperion going to give me an OS I can buy to try this out on? ;-)
Edit: Actually, scratch that - after looking more carefully, it looks like it's all just generic engine code - for example in game.c there's mention of "brown monsters" and "evil al", but none of the the usual Duke3D menagerie. Looks like I was wrong. Nuts :-(