Neither the amigaOS 4.0 or MorphOS (Pegasos is the name of the hardware that Morphos runs on) will run on UAE for mac. UAE emulates the 68k hardware (custom chipsets etc.) while the above mentioned OS'es are PPC native. The best chance you can have is that some "pirate" group wil make a solution like MacOnLinux but the other way around (morphos on mac) OR an installer disc that tricks the proprietary dongles on the mac firmware and installs Morphos while the firmware thinks it's installing MacOS X. AmigaOS doesn't have a chance going to the macs. Even for Pegasos the chances are quite slim.
If I'm wrong to any of the above, please correct me :-).
