The way I see it is this: If the developer sold 100 copies under the old agreement, then no one else wanted to buy the product, they would have to support it for the 18 month period under the terms. The fact there is a new agreement they don't agree with just prevents them from selling anymore. They should still be supporting the product for those that purchased it under the existing agreement etc. If they don't agree to the new terms, they should make their own store etc. and sell it that way, but still need to support the initial customers.