The repository is accessed using SSH with key authentication. Send your public key file (id_dsa.pub) to Jörn Reder <joern AT zyn DOT de>, who adminstrates the CVS server. Jörn will create an account for you installing your public key as an authenticated key for passwordless authentication. (But note before you request a CVS account this way you need to be a transcode developer already and if not you should contact the developer mailing list ;)
Then edit or create the file ~/.ssh/config on your lokal workstation and add a section for cvs.exit1.org:
Host cvs.exit1.org Port 19471 Compression yes CompressionLevel 3
This sets the SSH port to 19471 (since cvs.exit1.org doesn't listen on the standard port 22 for security reasons) and enables SSH compression, so you don't need to enable compression on the CVS level.
Now you can access the CVS repository as usual:
cvs -d YOURACCOUNT@cvs.exit1.org:/cvstc co transcode