CVS access is provided by SourceForge.net, so if you're familiar with that whole setup, you're in good shape.
You can view the CVS tree here. The stable module is, dada_mail_stable
Log in first:
cvs -d:pserver:anonymous@mojomail.cvs.sourceforge.net:/cvsroot/mojomail login
The password is blank.
Then export:
cvs -d:pserver:anonymous@mojomail.cvs.sourceforge.net:/cvsroot/mojomail export -Dtomorrow dada_mail_stable
(all on one line)
At the moment, I'm using MacCVS Pro 3, which is working fairly well with Mac OSX Panther, although it does have that, carbonized-in-a-hurry OS 9-ish feel. But hey, it's free and has some fairly nice integration with BBEdit and is snappy to boot. BBEdit 7 itself has limited CVS support, but I'm still on version 6.5.
I used to use jCVS when I worked in a mixed environment. Since it's written in Java, it'll run on anything with a Java interpreter. It's a bit sluggish in OS X, but it's customizability it fairly sweet. I haven't been able to use it for Dada Mail, since I have yet to figure out... how to customize it to work with SourceForge.