I used to have powermac and I remember that in order to boot from Mac OS install CD, powermac had to be equipped with genuine cd-drive with apple firmware. How does it refer to MorphOS?
That's a first time I hear about something like that: I have a Sony dvd drive in a PowerBook and some replacement drive in a Mac mini and had no such issues. Surely if the drive is detected by OpenFirmware, you will be able to boot MorphOS from it. If not, MorphOS can also boot from USB on many Macs or even over network.