I can see the DOM's partitionms in HDConfig. And I can boot from the DOM into Linux, so OF must see the partitions.

Hmm, how can I check if MorphOS wrongly recoznizes the DOM as read only?

@Norbi:
What MorphOS bootmenu? I use yaboot for the time being, but I can check if the OpenFirmware bootmenu lists the Linux HFS boot partition. There is no MorphOS HFS Boot: yet, as I am not able to create one.