OpenCA has rpm for FC4:
https://www.openca.org/projects/openca/downloads.shtml
Will that work for Centos 5?
Gee I should just spin up a box, try it and see if it crashes and burns.......
Given the interest in OpenCA in edu and k-12, it would be nice to see this readily available. Of course I am biased, as I lurk on the various edu PKI forum.