Occasionally people ask me or just mock me because we’re still using CVS in the curl project, even though there are much more compelling alternatives out there now. Subversion, git, Bzr, Mercurial, etc. I am even a contributor and committer in the Subversion project. (Although I’ll be the first to admit that I never committed much and the stuff I did was done many years ago.)
CVS just isn’t bad enough to warrant the work of a replacement. curl is a tiny project (source code wise) and while CVS has several flaws in how it is designed and works, those flaws never hurt us much. Basically the only one is the lack of rename support and that has no major impact on us.
On the contrary, CVS has the upside of being established and rock solid since many years so people on all sorts of platforms can use it and get the curl source code. This is important especially for our automated build-system which we try hard to find volunteers for to run automatically daily around-the-clock (the results and outputs are then mailed to our central autobuild master server that collects and presents them) and then those guys need to be able to checkout the code easily. Using more modern tools will make it harder since those aren’t available as widely as binary packages for as many (outdated) platforms as CVS is.
So curl sticks with CVS for now.