John,
CentOS 5 is almost exactly the same as Red Hat Enterprise Linux 5
(CentOS site claims binary compatibility). CentOS5 is also very close
to Fedora Core 6.
Normally software named EL5 and CentOS5 works on both. Something
packaged as FC6 usually works with some hacking in general. Because
anyone can build a package there are no universal truths.
These should help.
http://linux-vserver.org/Installation_on_CentOShttp://linux-vserver.org/Installation_on_Fedora