Back on the subject:
UAE on Gameboy DS: wasn´t somebody going port UAE to the GP32?
Or rather rewrite? if the 133Mhz GP32 can´t do it then there isn´t any chance for a 66Mhz Gameboy DS?
AROS on Gameboy DS: IF somebody gets linux on it you could make a hosted version. Native isn´t worth the effort.
But why Gameboy DS?
Me, I would get something based on NanoITX instead. 533Mhz 1024MB RAM running WinUAE or native AROS with AROS-UAE. :-D