Besides the source code management systems covered in this book, several other systems are worth knowing about. The following list, though, is by no means exhaustive:
GNU Arch is a distributed source code management system similar to CVS and Subversion. One of its significant strengths is that you can do offline development with it, working on multiple versions even on systems that are not connected to the Internet and that cannot communicate with the central repository. For more information, see http://www.gnu.org/software/gnu-arch/.
Codeville is a distributed version-control system in the early stages of development. It is written in Python, is easy to set up and use, and shows a lot of promise. For more information, see http://codeville.org/.
CSSC is a free clone of SCCS. It intends to provide full compatibility with SCCS, including file format, command names and options, and “bug for bug” compatible behavior. If you have an existing SCCS repository, you should be able to drop CSSC into your environment, in place of SCCS. CSSC can be used to migrate from a commercial Unix system to a freely available clone, such as GNU/Linux or a BSD system. For more information, see http://directory.fsf.org/project/cssc.
The web page for monotone describes it well:
monotone is a free distributed version control system. It provides a simple, single-file transactional version store, with fully disconnected operation and an efficient peer-to-peer ...