The CoreBoot (formerly LinuxBIOS) port is being actively developed. Make sure you're always using the latest CVS.
For CoreBoot v2, you might need the phdr patch from http://lists.gnu.org/archive/html/grub-devel/2007-10/msg00056.html
Build instructions:
./configure --with-platform=linuxbios make ./grub-mkimage -d . *.mod -o path/to/payload.elf
It still has several issues, among them the lack of timers, making the ATA driver fail (except on QEmu).
Also see the Coreboot page on GRUB2