Trac is a minimalistic web-based software project management and bug/issue tracking system. It provides an interface to the Subversion revision control systems, an integrated wiki, flexible issue tracking and convenient report facilities.
Trac is distributed using the GNU General Public License.
You might also want to take a look at the RELEASE and ChangeLog files for more information.
Otherwise, the primary source of information is the main Trac web site:
We hope you enjoy it,
/The Trac Team