The shortcomings of CVS have led to the development of other systems, with one of the most well-known being Apache Subversion (SVN). In addition to the improvements it has brought, it was specially ensured that is has high compatibility with CVS. It is also open source licensed (with an Apache license, not GNU). It was started in 2000 by Collabnet Inc., but changed to an Apache project in 2009. You can find it at https://subversion.apache.org.