I see, so AROS would be the only real option for these ARM powered devices.
Sure I'm biased, but AROS is the only real option full stop
Is there any documentation about how to recompile the kernel for BB? the Pi is cool but it is a bit underpowered, and the BB is much faster, which makes it more likely to be able to run software better and faster.
Pi underpowered? You'll struggle to find as powerful a computer for £20... Also, IRC, the BB has weaker GFX performance than the Pi
For the money, the pi is the best option IMHO. -edit- the BB is really for electronics/hobby prototyping. The pi is a consumer electronics device.
Heck, if it run on my 030-50MHz, should run nicely on a GHz processor with accelerated GPU 
Also I heard about Minimig; and was wondering what is the os that is running on it....conceptually seems like a pi or a BB.
Minimig is something else, basically an A500 on a single chip (two chips if you include the 68000)... It will run the original AmigaOS and the 68k build of AROS.
