Yes, Be could swap code for the specs to the G3 motherboard (its the support chips, not the G3 itself that Be can't support) but then you have code hanging on a shoestring. In Linux, this is acceptable, but Be has tried to avoid "hacking" code to make it work.
Besides, Apple could turn around and sue, and who wants that. LinuxPPC doesn't have much to worry about, but Be is a corporate entity and subject to a different rule book.