Philosophically and economically, trying to sell a product without alienation, that is to say by keeping some rights on the future use of the product, is quite dubious. Let's say you produce a very nice car which, for some reason, you think does only look good in red. You will decide to only sell this car to people who will agree to sign a contract which will forbid them to paint it in any other color. Although it might seems ok, I would have much difficulty to blame anyone who would sign the contract, but who, as soon as the seller is away, would paint the car in blue.