One of the BBC engineers compiled Dream for OSX (some years ago!). He had it working on a 1GHz Powerbook, although the Powerbook would not run much else when Dream was working.
Also he had to use an external soundcard as there was an issue with the apple sampling frequency 44.2 kHz (or something like that) whereas a PC soundcard will do 48kHz. someone with enough expertise could overcome the soundcard problem with software by resampling. If anyone is seriously interested in compiling Dream for OSX (it is not a small undertaking) please put a post on the Dream forum and let me know.