Being someone who loves their iPhone I would start by calling AT&T to see if the owner has reported it stolen/lost, then I would ask the AT&T about how to return the phone to the person who paid for it.
Wouldn't you want it back if you lost it?
an iphone (8gb) was given to me which was found by a friend while jogging 3 months ago. No one claimed it so iphone was given to me. How do I activate if I just want to use it like an itouch? I don't want to sign up with AT&T for cell phone service.