Does it work? The answer is yes! 
All you have to do is edit the sshd_config file on the OpenBSD machine and set X11Forwarding to yes, then fire up X (I’m using XQuartz 2.3.2 (xorg-server 1.4.2-apple18)) and in an xterm (or Terminal.app!) enter
ssh -Y user@openbsd_machine program
Voila!
P.S.: Actually, you don’t even have to start X on either end of this connection, it will still work. I just tried
If you installed Security Update 002 for leopard and suddenly ssh tells you “bus error”, the answer lies here:
http://discussions.apple.com/thread.jspa?messageID=6863360#6863360
Apparently the guys at rogue amoeba have some work to do – we need instant hijack!
If you are too lazy to read that thread, the fix is:
sudo /usr/local/hermes/bin/hermesctl unload
thereby uninstalling instant hijack and fixing the problem. Somehow…
… and here’s the fix from Rogue Amoeba:
http://www.rogueamoeba.com/utm/2008/03/19/security-update-2008-002-compatibility-fix/
