1) Read the licences that surely must come along the software (at your friends' if noplace else)
2) Contact RedHat and ask them what the licence says about usage; most of the software is open source so it shouldn't pose a problem, but their licencing may contain stuff that you can't use without paying.
3) No geek here knows well enough compared to RedHat customer service. Send them an email and ask. If you're afraid to say you've been running the server already for two years, you can always say your friend's in the situation or that you were "thinking about it"