I’m not convinced there’s any need to try preventing downloads from other sources. It would be a place people can upload their work to if they want to share it, for sale or not. If it’s for sale the most sensible thing is for the author to not upload somewhere else. You can’t stop piracy and ‘free spreading’ – none of the online stores have found a way to stop that! There are after all a great many things about online stores that people really don’t like – DRM being a case in point.
Look at WHDload – most genuine Amiga supporters are willing to pay for the registration of a product they find genuinely useful and enjoy. Yet WHDload remains freely distributable in unregistered form.
Perhaps certain types of ‘licenses’ could be developed. I certainly would expect to pay someone for a hosting a product I’m trying to sell- I really wouldn’t think otherwise.