Monotone
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 synchronization protocol. It understands history-sensitive merging, lightweight branches, integrated code review and 3rd party testing. It uses cryptographic version naming and client-side RSA certificates. It has good internationalization support, few external dependencies, and runs on Unix, OSX, windows, and is licensed under the GNU GPL.
Homepage: http://venge.net/monotone/ 1
Analysis of features (mainly based on VersionControl): wiki:EvaluationFeatures 1