User-space daemons - which will compile up on any *nix system with little work.
The hard bit to port, is the "pseudo hba kernel module'.
I didn't even worry about trying to get it to backport to the 2.4 kernel (not that it is important nowa days).
If you know something about kernel module (SCSI LLD in specific) for BSD (free or otherwise), feel free. I'd love to see it done.
For that matter, the user-space can be ported to any OS which has a port of gcc. It's the kernel module to get those SCSI packets from the SCSI stack out to the daemons.. Perhaps I find it hard, as I do this for 'fun' and kernel level programming requires skill & knowledge which I find outside the definition of fun ;)