Startup Disk does not see it as bootable. Holding down C gives up and ejects it. I have tried PPC version of CDs for both Lucid and Maverick.
The machine is a 867 MHz PowerPC G4 with 512 MB RAM.
I Got the ISOs here and here
Boot to OpenFirmware, then boot the CD from there.
I find that my G4 PPC won't boot from CDROM/DVD, in fact it's pretty fussy about reading a lot of newer optical media.
The easiest is to create a bootable USB stick. This will involve a having to boot it from the OpenFirmware prompt. There is a good guide available.