It's not that he has some inner urge to contribute in some way, he just encountered a bug while using the software and wants to report it. The alternative isn't coding — it's no contribution at all.
Unless you only ever work on projects that you have full absolute control over (unlikely if you have a job) then yes they absolutely are.
You can clone the other person’s apartment for free and do whatever you like, though. Just don’t barge in to someone else’s apartment and demand they treat you, a stranger, like if it were yours.