Weird that they won't ship TMNT stuff your way, but they can ship others.
I haven't been to any HT in awhile, though both stores that I frequent at the MOA and in St. Cloud are still around. This is honestly the first that I've heard that they might be ripping stuff off and blatantly using them on T-shirts and other merch. When I lived in St. Cloud and bought stuff there more regularly, I was under the impression that it was all licensed, as surprised and delighted as I was to see TMNT shirts I could actually wear as a grown up.
I'd have to dig up the shirts I haven't packed away(heh, I was wearing them out

) and look at the tags, to see if the company that made them is still in existence and if they ever did hold a license to make and sell the shirts. That's the best I can do, since, like you, I have to travel a few hours to get to any HT stores.
I can also ask Earl to look into it. He has much better luck tracking down stuff online than I do.
It does seem a bit odd and suspicious that for all the stuff they ship your way, TMNT is the one thing they won't.