I've got an experimental version of Pd compiled for imac available on http://crca.ucsd.edu/~msp/software.html ... unfortunately, since it seemed advisable to update portaudio to the new, completely rewritten one, it would be unwise to retrofit this to Pd 0.39 (might change latencies or other things for pre-existing platforms).
I made up a new file extension for externs (pd_imac) ... we could always go to a "sensible" naming convention in the future and stay back compatible, if people think it's too ad hoc. In the long term, the set of architectures/ OSes seems set to stay at around hald a dozen active ones, so there's no big problem just making up names unsystematically.
The only other policy implication is this: I'm using files from the supplied "Wish shell.app" on Imac, which seems a reasonable thing to do, but strictly speaking it's probably more correct to download a bsd-licensed wish shell or recompile it from source. That shouldn't be too difficult to do, I hope.
cheers Miller