No installing on ext3. No installing any more on UDF
"**Is there any working group that use Darwin's XNU to create distribution? I know openDarwin, but they stopped." MacOSForge.org has Xnu development. It seems Apple employees are picking up some projects (including Darwin Ports, renamed Macports) that OpenDarwin used to develop.
Most linux distros, and other operating systems for PCs try avoid microkernels now because they have been shown to have serious problems. I think HURD project tried to switch from Mach microkernel to L4 microkernel?!?! Minix3 has just come out with a microkernel, but I don't think its xnu.
I'd also like to boot Mac 10.4 or 10.5 from GRUB and especially Grub2, , but I don't have the time or inclination to experiment. I do know that 10.5 has dropped support for UDF file system, and its likely that Darwin 9 will not boot from UDF either. UDF was the only other filesystem OS X could be on, but UDF never has been standardized, and I think Next's/Apple's UDF was different than NetBSD or FreeBSD.