To boot from CD
 > boot cd:,ofwboot.xcf netbsd.macppc

To boot from ofwboot.elf on HFS and kernel on CD,
 
 > boot hd:,ofwboot.elf cd:,netbsd.macppc

I have not tested these command, but writing from my memory,
sorry,

You need colon(:) to say the string to left is device, but you may
omit the partition number right to the colon.

See also:
http://www.ki.nu/software/NetBSD/iBook2/
---
(Makoto Fujiwara,Chiba Japan)