What about adding FreeBSD to it? FreeBSD 's got a version for PowerPC and if you prepare 7 partitions it runs perfectly but you should best use gpart for it. In case of mystery, the 7 partitions are:

1- Bootcode for FreeBSD
2- / (root directory)
3- SWAP
4- /tmp
5- /var
6- /usr
7- /home

Actually you don't have to add /home but it's better for completeness.

I have prepared a multi-boot MorphOS and FreeBSD harddisk on my Mac mini G4 but MorphOS install (it's called IWizard, lWizard?) didn't like this scheme of partitioning. MorphOS install gives this error:
No HFS (Mac OS standard) partition has been found

though I already prepared and specified a HFS partition using this guide: http://library.morph.zone/Dual-boot_MorphOS_and_MacOS_X_on_a_Mac_Mini_G4

When I did the partitioning in Mac OS X Disk Utility, the MorphOS install didn't get stuck at this point (it was a Ubuntu - MorphOS dual boot) but partitioning for FreeBSD is a bit awkward to precisely make 10+ partitions.

Help and advice is needed.