@Agafaster
cos they own the hardware, no matter how 'obsolete', and the rights to decide who runs what OS on it.
No, they do not have the right to block any OS running on their hardware, and they don't even try. They DO try to block Mac OS X running on non-apple hardware, however (and years ago Apple stopped mac clone business).
to do it properly, IIRC, would require hardware documentation ?
You can use open source operating system implementation as a reference. Many components (such as graphics cards) are the same as on PC, anyway, so they're no problem. Some hardware might not have any drivers at all, though (wireless networking hw drivers for example).
as a side note, I would be interested to play with Morphos on my A1
MorphOS requires working cache coherency (just to mention one reason why you won't see MOS on A1).