Hi mate, been a while since I saw you post :-)
I wouldn't doubt that AROS will run on similar machines eventually, I don't know however if they have such a machine to build for and test it on, you could always lend them it for a while ;-)
As for BeOS, I seem to remember reading about a PPC port that was never completed, however there is OpenBeOS, one of the target architectures for that project is the G3/G4 iMac. As far as I know, Zeta (the new name for BeOS, esentially) is x86 only.
