Littman's innovation isn't really the format conversion, but the single-window, parallax-corrected rangefinder-viewfinder. The thing that seems egregious is that he's tried to use his patent to corner the market on old Polaroids, to prevent others from doing whatever kinds of format conversions they want with them, even if they don't have a single-window parallax-corrected rangefinder-viewfinder.
Littman's conversion seems more capable than the others I've seen, so you might think he would be content just to protect his specific innovation, which requires some more sophisticated engineering than a straight conversion, and costs more as one might expect. If others want to do straight conversions for customers who can't afford a Littman anyway or don't really feel they need a single-window parallax corrected rangefinder-viewfinder, why should he worry? It's not as if old Polaroids are such a rare commodity, or that the demand for such a thing is so immense.