[wp-hackers] Libertus Anti-Spam?

[Computer Guru]

Someone help me out here.
Is this for real? 

"Based on a denatured version of Akismet, my anti-spam plugin tests whether
each comment can be compressed, and if so, by how much. Comments that
compress 5 or more times are marked as spam."

The guy's site is down..
http://libertini.net/libertus/wordpress-plugins/anti-spam
DL @ http://wpplugins.org/plugin/libertus-anti-spam-compression

Am I the only one that's lost?
Text compresses. The more text you have, the more you can compress it. 
Where does spam come into the picture? Is this assuming that spam is the
only comment long enough to be compressed?

Or am I forgetting something?

-CG