Just to make it clear, here are the commands you would issue to checkout from anonymous CVS on the *NIX commandline:
cvs -d:pserver:email@example.com:/cvsroot/post-nuke login
cvs -z3 -d:pserver:firstname.lastname@example.org:/cvsroot/post-nuke co -P modules
Currently, the only module available is the Google Search.
To use these modules, just drop each directory into your modules directory ie:
if your Post-Nuke directory is at /home/postnuke/public_html/ and your modules CVS directory was at /home/postnuke/cvs/modules/ then you could "install" the Google Search module by issuing this command:
cp -R /home/postnuke/cvs/modules/Google_Search /home/postnuke/public_html/modules/