okay, here's a list of coins generated via coingen, as maintained automatically by the coingen site.  I haven't listed all of these because with a lot of them there's no evidence that they even launched. 

http://coingen.bluematt.me/status.html

Gamecoin, Cloudcoin, Doubloon, Onecoin, and Americancoin have definitely  been generated by coingen.

If there've been multiple coins by those names, then certainly the fact that at least one of them was a coingen coin is an important part of the history, and may be one of the reasons why it's dead.  And honestly it doesn't matter which of them was the original; this thread is only about which one is dead.

No, tax coins are sold to gold. You only pay capital gains on the amount of price increase of your gold after you've bought it.