It depends. Is he just adjusting his junk? Some guys seem to do this way more often than necessary. Or, is he grabbing it (not to adjust, but to make it known he's grabbing it, and possibly shaking it a little during the grab)? If that's the case, then I'd say he most probably wants you.
Here's a good way to find out. It could also make for a really hot story. Somehow let him know you're gay, without it being obvious that you might be trying to seduce him. Even better if you somehow arrange it so that he finds out and thinks that he doesn't know. Try leaving this site, or some other obviously gay site, open on the computer for him to find, or something like that. If, in fact, he does want you, and isn't just adjusting his goods way too often, then you've already planted the seed at this point. Finally, one night, when just the 2 of you are around, get a little drunk. You should act like you're more drunk than you actually are (or why not? just get drunk) and get a little touchy and in his personal space more. Find any excuse to touch him, and exploit it. If he does want you, then he'll probably let it be known at this point. He might reciprocate the touching and maybe linger a little longer than usual, kiss you or go all the way. who knows? Or, he could just be straight and you're misreading the signs. In that case, you can just play off your "probably too intimate" actions as being drunk.