Pius source can be checked out via anonymous CVS on the Sourceforge CVS repository. The repository is :pserver:anonymous@cvs.pius.sourceforge.net:/cvsroot/pius and the password is an empty string. (Just press Enter when you are prompted for a password.)
Developers can use SSH to get read/write access to the repository; the CVSROOT for the repository is then :ext:username@cvs.pius.sourceforge.net:/cvsroot/pius
Only actual code is kept in CVS; theme data is stored on the webpage.
Releases are tagged in CVS using the following format: pius-version-rel; for example, the tag for version 0.4.1 would be pius-0_4_1-rel