The Xfce subversion repository is the location where all Xfce components and applications are developed. It’s a collaboration system that uses subversion to allow multiple people access to the same source code, and work together on it at the same time.
You can browse the repository online here: http://svn.xfce.org/svn/xfce/ and http://svn.xfce.org/svn/goodies/
You can also use the web interface to view diffs, logs and meta-information stored in the repository here: http://svn.xfce.org/