Here's an idea: boycott any makers/designers who market such fabric. If I pay MY money for something, I will do whatever I please with it... whether it's for myself, for a gift, or for sale. But if you insist on buying such fabric, please consult with your attorney to see what your options and limitations are. I cannot see how a manufacturer or designer can legally specify how one is to use their fabric... a free pattern, ok... but fabric one buys? Hardly!
Guerilla Granny on a soapbox (again).