Is he interested of just simply being friendly?

He might or might not be interested. Even though he has a girlfriend, relationships don't last forever. Look at the divorce rate. My parents got divorced after 12 years. So I'm just saying, relationships don't last forever. Also, guys generally like other girls even if they're dating. But who knows. If he feels comfortable talking to you about "certain things" then he might like you back. You can never tell how a guy truly feels. They don't express emotions well. Don't think he's out of your league. That's just hurting your self-esteem. He could like you. Look and labels don't matter. Just kind of go with the flow and see where he goes with it.

He just likes getting your attention but probably has no real interest in you. And if the things are "inappropriate" that you do ,then you should stop doing them because you guys are making yourselves look bad. Do you want to be known as the type of girl who is always messing with taken men? Does he want to look like the kind of guy that fools around on his girlfriend? I would stay away from this guy cause he just sounds like trouble.