I'm willing to bet that the threats of going to court are a bluff, as he would have to either hire his own lawyer (this would be a small claims court issue) or fill out all the forms and file them and pay the fees himself. However, I agree with everyone else that it's just not worth the bother, because if he does fill out the forms and file the claim himself, he'll do so so where he lives and does business and you would have to defend the claim there. If you ignored the claim, the court would find against you and you'd be out of luck.
I especially like the idea of different bar code stickers for the different production runs of the module. And since bennybingo says that lots of other businesses do it this way, it will still have an authentic look to it.