Although its adsense based, it runs of a diffrent program, the keywords for parking our pulled from teh doamin name or keywords posted to the google servers.
Where adsense is based on content. Also sedo run a difrent system from all other google parking members which gives them live stats etc, wehere for normal parking members update is every 24 hours etc.
Sedo use a keyword system where you enter a keyword and google shows them results.