The wikipedia article could in no way be summarized as "we let Korea print $100 bills". A first sentence is "A superdollar (also known as a superbill or supernote) is a very high quality counterfeit United States one hundred-dollar bill,[1] alleged by the U.S. Government to have been made by unknown organizations or governments". The body of article follows this. Only dubious allegation that North Korea (among several groups) print them and no allegations that the US allowed this.

Link if it gets lost: https://en.wikipedia.org/wiki/Superdollar

I am having trouble finding the 'let them' part. I see plenty of allegations. I just wanted to find out when the US was 'off the books aiding' North Korea.

Outside hot-war which would result in massive casualties in SK, there is very little more that can be done to NK...

So there being no choice is probably correct in this case. At least with other countries there is some ways pressure them, with NK not too much, and not for measly sums of money involved.