I think you need a law degree to understand the rift between Hyperion and Amiga... But here's my uneducated $0.02...
I think legal is the barrier, as there isn't anything too terribly technical that would prevent it.
Hyperion is on record that they don't want to compete with windows, and they see locking OS 4 to hardware (specifically proprietary and not x86) their only option.
Hyperion has also stated they believe Aros, and other Amiga "clone" OS's to be illegal. (at least as far as they are concerned)
