Perhaps this dude won't mind, but my gut tells me he will. There are some things you can do when you live alone that you cannot do when you have a roommate. When I was fresh out of college I lived in a situation with 2 roommates (we had a huge apartment). Anyway, one guy was cool and considerate, while the other guy was a complete muppet. He was a fucking weirdo trying to sit around in the common living area in his briefs as if somebody wanted to see that shit. One time I was in the shower, when the next thing I know its this asshole yelling "I think I left my wallet in the bathroom, I'm coming in for it." To which I promptly warned him of the consequences if he did. Needless to say, he did not come in for his wallet.
Anyway, I'm off the subject, but the point I'm making is you may want to check with the guy first before doing some objectionable shit like riding the upholstery with your unclothed ass. If it were me that shit wouldn't fly. Nobody but nobody wants to sit around on a couch that has been pre-sat by a bare fuckin sweaty ass, unless they're fucked in the head.