Judging from the post here
http://forums.fireflymediaserver.org/viewtopic.php?t=6920&highlight=leopard
you should be able to get 10.5 running if you take svn1586 from the nightlies site: http://nightlies.mt-daapd.org/
I don’t have 10.5 yet on my mac so can only advise from what’s been posted. Search under ‘leopard’ for other users’ experiences. However, if you review the post that EVILripper linked to above with the stuff I bashed through with someone else trying to get them up and running then fingers crossed you’ll get there. Bear in mind that was quite a few months back so svn versions etc have moved on but the basics remain the same.
Couple of things to bear in mind: you’ll probably find that the first time you perform a scan it’ll hang on startup. Let it run a while then stop and restart and it should then indicate in the preference pane that firefly is indeed running.
Make sure you open up a port in your firewall. Also make sure you shorten the self-assigned name that firefly gives – if it’s long then firefly can’t handle it & won’t play.
Holler if you need more help. 😉