That is called "white-labeling" and it happens quite a bit. Some generic brands at the grocery store are white-labeled brand name product. Generally it is done by agreement with the original source, but it doesn't have to be done with their permission. Without more, I think it would be hard for you to prove you have been damaged, since he paid for your product and you can resell product that you buy. Software products that are not sold but licensed instead can stop that from happening, but if you are selling a physical good, then you should probably just be satisfied that he is paying you for product.
Answered on Apr 18th, 2013 at 8:51 PM