The Sparc Improved boot LOader is a GPLed program most commonly used to boot Linux (or GNU/Linux if you prefer) on Sun's SPARC hardware but it can be used for SunOS and Solaris as well. SILO is actually stored in PROM and can be used to select an operating system during boot in a similar fashion to LILO. SILO supports ext2fs, ext3fs, ufs, romfs and iso9660 file systems.
The program and more information can be found at http://linux.auxio.org/silo/