PRCS, the Project Revision Control System, is a version control
program with purpose similar to that of CVS. It was designed
with simplicity in mind. Like CVS, PRCS uses RCS to accomplish
this task, but this is inconsequential to the user, as RCS is
completely hidden beneath a layer of abstraction.
PRCS has a website on SourceForge at http://prcs.sourceforge.net/.
It can be downloaded there.