Overture was sold to Yahoo in 2003
http://searchenginewatch.com/showPage.html?page=2234821
If you are an advertiser looking to drive traffic to your site
you probably want to sign up here
http://www.content.overture.com/d/
If you are a publisher looking to do PPC you're after YPN
http://ypn.yahoo.com/ which is very difficult to get.
Adsense is a Google product and competitor to overture/yahoo
http://www.google.com/intl/en/ads/ approval is usually completed within days
Good Luck