I've been looking at your plug-in page and that's pretty interesting.
So in fact there are 4 products (1450, 1451, 1452, 1453) that could qualify you to checkout OR the proof of purchase code.
I'll give it a whirl and see where it goes. I wouldn't mind paying for or donating to such a thing. Do I need the Min Pro version to apply to all the contents of the cart?