Update: He wasn't picked up yesterday and we haven't been able to get in touch with his owner at all. Next step are the certified letters (to be sent out in the next week) and then if we still haven't received any contact he will be surrendered to the clinic. So, it is looking very, very likely that he will need a home. If whomever is interested wants to start making tentative arrangements for him, that would probably be a good idea so when he is "offically" abandoned we can get him moved asap.
And just a bit more information on him - he does appear to be crate trained. We're booked up over the holiday weekend and since he isn't a paying client he was bumped out of his suite and put into a grooming crate until we have a run open up again. He barked when he first went in, but he's been just chilling out all day.
He's very bright and picks up on things really quick, and is really intune with whoever is handling him.
He is aggressive with other aggressive dogs. He is fine with friendly dogs/dogs that ignore him, but if he gets lunged at he'll lunge right back. He hasn't been fond at all of other intact males we have had come through the clinic, but I haven't seen him have a problem with neutered male/female dogs unless they are trying to eat him through the fencing. Even then, he just barks/lunges and isn't out for blood. But I would say he isn't going to be dog park quality.