Well, the otheros.bld is just a compressed linux bootloader, all the technical stuff is in the Cell ADDON CD, its all you need, has all the source code etc. That, and the IBM Cell SDK.
As for porting OSX over, it has been discussed in another thread, needless to say, its not for the new user, it would take a dedicated coder, atleast a while to port it over.
And technically, windows was in a PPC variant, NT 4 (or maybe 3.5), in which the Xbox 360 kernel is very loosley based off!
Moved to Linux chat too!