Overlord is sold through a partnership with torquepowered.com. A free account is required, but this will give you access to the torquepowered.com community features such as blogs, resources for game development, and very active forums.
Just wanted to let you know I use PHP Overlord Extensively while producing our XBLA and other games here. Great stuff!-Tim Aste
I highly suggest picking up Overlord, it's done wonders for our team.-Coleman
Purchasing Overlord was the smartest move we ever made, our team is working faster and better than ever before. 10/10-TKAzA