The way RedHat does it is to give you "entitlements". You can look at their site
www.redhat.com looking for "RedHat Network" information.
So far as I know there is no actual "license" file installed on the individual servers.
Also note there is a change: Prior to RHEL up to RedHat 9 you could use "RedHat" for commercial or non-commercial purposes so didn't require a license. Starting after that with RedHat Enterprise they separated out so you should have a license for RedHat Enterprise but can use Fedora Core without a license. Fedora Core serves as a testing ground for what ends up in RedHat Enterprise. With RedHat enterprise (RHEL) and Fedora Core (FC) they started renumbering the distributions at 1 again. RHEL is now up to RHEL 5 and FC is up to 6 (I think FC 7 beta may be out).