Hello,
Fossil (http://fossil-scm.org/) is a mature, fully-featured source code management platform, including its own DVCS, a Trac-like ticketing system, and a wiki. It is actually the SCM used by SQLite and Tcl/Tk, which is as traditional as it gets. It's also very scaleable and space-efficient.
It would be lovely if SourceTree supported Fossil in addition to Git and Hg. You probably have a lot of the infrastructure done already, and it only helps that the Fossil license is BSD-like.
Thank you for considering!