Sure, it's just the same as "moodle", except use "mysql". You can also do "docs" and "contrib".
cvs -z3 -d:pserver:anonymous@cvs.sourceforge.net:/cvsroot/moodle co mysql
cvs -z3 -d:pserver:anonymous@cvs.sourceforge.net:/cvsroot/moodle co mysql
Why such things are not documented? I mean posted on the installation page?
Accidently, I found the proper documentation on CVS, answering all my questions, in the section of this site for developers. The installation instructions should include at least some of that or there should be a reference to go to CVS info for developers. As a site admin, I did not venture to developer area looking for such info.