However it CAN be a good model as many rendering application does this. Even a funny thing happened once in the Twilight Forums (it has resolution limitation AND watermark) a guy came and complained that he cannot export larger than 800x600 pixels and the answer was that surely he cannot with pirated versions. That must have been the case as he never came back...

They also have a computer specific licensing method and the key will only work on one computer with a certain OS install (so if you move to another computer, change hardware or reinstall OS, you need to get a new auth key) These are all good ways to minimize piracy (cannot fully eliminate it of course) but when it is so cumbersome already, users will tend to rather buy the product - especially if it is so well priced as PhotoSculpt (or in fact twilight, too - exactly the same price
