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.
You can download the complete repository in .zip format: https://sourceforge.net/code-snapshots/cvs/a/al/algol68.zip
Once you have downloaded the file you can unzip and checkout a working copy with the following command cvs -d /full/path/to/algol68 co algol68
