There's a hosted version of AROS for the Raspberry Pi that might also work on the BeagleBone. The problem with the ARM-native version of AROS is that it's based on the unstable branch that has yet to be finalized. This means that it may not be ready for any closed-source projects yet since compatibility-breaking features may yet be introduced, thus requiring a recompile.
The problem with trying to port an operating system to a new processor is that some of the parts of the program are written in raw machine language instead of compiling languages like C. AROS was designed to be portable from one architecture to the next and as far as I know, it's the only Amiga-like OS to run on the ARM architecture.
