Yes most men like to dry hump
No it dose not necessarily hurt at all, it is like anything if rubbed too much it will hurt
You will know soon if it is hurting him he will go soft and limp very fast
Conclusion to your question dry humping if fun and is good for both sexes

> Do guys like dry sex /dry hunping?

Absolutely, positively, indupitably, yes.

> I mean I was straddling my boyfriends waist and we were dry hnping and he seemed to like it cause he was breathing hard and groaning but I heard it hurts them too.

Not really unless you are pinching or squishing something.

> I heard that the jean can sometimes leave burn marks on rashes.

Probably possible because the material is more abrasive. If he is wearing underware, I rather doubt it unless the activity goes on and on and on. Take your cues from him.

> I mean I know (well I think) he likes it but if its going to hurt him I dont want to do it.

Take your cues from him on what to do and perhaps change.

Dry humping can be a very fun and enjoyable activity. Most likely it will not hurt him unless it goes a long time. This can also be very stimulating for the girl also, so hopefully you both get something out of it. See if you can make him cum from this as a little bit of a goal.