Is this a Stack Exchange website?
I recently stumbled upon Draw 3 Cards, and would like to know if it's one of your sites. If it is, why isn't in the site register? If it isn't, why does it use your engine?
Draw3Cards is a Stack Exchange 1.0 site, from the model back when it cost money and there was no proposal process. This means they use the engine from back when Stack Exchange 1.0 was in activity, but are not considered a part of the Stack Exchange Network that comprises the Trilogy and all Stack Exchange 2.0 sites.
I recommend this blog article on the shift to 2.0, if you want to read up on how 1.0 and 2.0 differ.
There was some discussion about its migration, but I believe that site had decided to stick with Stack Exchange 1.0, possibly due to the unwillingness to be merged with Board & Card Games.