I have a beige G3, and there is not a dual boot loader that I've found.

i don't know much about this topic, but i do know that the ppclinux
booter (err, dunno it's name off hand) is able to dual boot macos
(9 or X) and linux.  i don't see why it shouldn't be possible to do
this with a smart enough ofwboot.

   And I don't think we'll find one. Mainly as MacOS X and NetBSD have
   different OFW boot requirements. MacOS X wants real-base set to -1
   (ffffffff) while NetBSD wants it set to f00000.
   
   I dual-boot, but it's a manual process. When switching OSs, I change
   real-base, then 'reset-all'. I'm aided by the fact I netboot NetBSD, so
   disk partitions aren't a problem.

i 4-way boot my G4/733 - linux, netbsd, macos 9 and X.  netbsd is the
only one that doens't boot from the disk (yet), but macos9 and linux
share one drive, and X and netbsd share another.  to boot linux or 9,
i boot from hd0 and it gives me the linux bootloader.  X is the default
boot, and netbsd requires "boot enet:0 ...."
   
   MacOS X uses a boot partition to help load. I experimented with an
   installboot that would move its boot partition before or after the MacOS X
   one, so you could control which OS booted. But I didn't get it to work. I
   now realize I had disk spin problems, so I should try again. :-)

please! :-)