I know this is a stupid question but I am confused about it. Thanks.
Almost every open source projects use CVS. Actually, I cannot think of any projects that do NOT use CVS...
It is a very nice tool to manage the "mess" you are talking about. The important thing is to not let EVERYONE have write access, since its dangerous (security-wise, people could add trojan in the code, for example) and it would make the project unmanageable). One way that seems to work great is to have a patch depository, and then some responsibles (the main developers) for the project apply (or not) the patch.
Most of the Blender USERS (read: not developers) shouldn't have to worry about CVS and all, as they will, most likely, prefer for a build. They way they can contribute is by submitting bugs. I guess Blender is best using Mozilla's Bugzilla. CVS is always too bleeding edge for stable production environment.
Look at other big projects on sourceforge, (www.sourceforge.net) for example, to see how they work...
NamShub