I'd have to say since the owner obviously doesn't care that you will have to try yourself to teach the dog some manners. If the owner doesn't like it then too bad really. You don't have a whole lot of options available to you and unfortunately it's really an awkward and frustrating situation for you.

I've read a few different methods of dealing with problem jumpers. The knee to the chest, painless but startling to the dog. Another I had heard was when the dog jumps up to hold its paws and keep holding them, the dog doesn't like that and begins to associate jumping up with getting "stuck," but you'd want to be sure the dog wasn't aggressive in any way for that... Maybe something that makes a loud, unpleasant/startling noise when he jumps on you or even a little squirt gun. Whatever you do I'd punctuate with the firmly spoken verbal command of "OFF."