It appears that reiserfs is suppored by 2006.0 on PPC, but when one tried to mkfs.reiserfs one gets the same results as doing a mkfs.reiserfs -V (i.e., only basic version info, nothing is actually done to create a reiserfs file system). This applied to the 2006.0 minimal CD (no others were tested). Work around is to go back to the 2005.1-r1 minimal CD where reiserfs works perfectly. (Have been using successfully for sometime on a G4).
It's compiled as a module into the kernel. Probably you need to run 'modprobe reiserfs'. I changed the size of a reiserfs-partition from the Minimal-CD. So the tools are working.
I'm guessing that makes this one INVALID.