Here's a video I shot some time ago. It shows my PowerBook G4 system booting up the MorphOS 3.0 (development branch):
PowerBook-G4-MorphOS-3-sneak-preview.mp4
Please note that this isn't official confirmation of any kind. A lot of support infrastructure for laptop usage is still missing, as well as some drivers.
PS. Sorry for the poor video quality.
PPS. We don't need any beta testers for the PowerBook version for now.
It's been over two years since I have logged in here, but I had to log in and reply. This is great. The Powerbook has been abandoned by Apple beginning with Snow Leopard, so I will be looking at Morphos when it is available for the Powerbook G4. I have two of them.