CVS is an old system for managing code. In order to access a CVS repository, you must install a CVS client.
SourceForge only supports readonly access to CVS now. For more information see our blog post about decommissioning CVS commit support. If you are a project admin, you can convert your repository to SVN or Git with these instructions.
This CVS repository can be checked out through anonymous (pserver) CVS with the following commands. The module you wish to check out must be specified as the modulename. See the names of the modules in this repository.
cvs -z3 -d:pserver:email@example.com:/cvsroot/cxbx co -P modulename