Mostly very well said TenZens. But I'm not sure if I really got that. Look what the one time payment for Prime includes between other features. It's a lot more then stated here from Uno. Especially the re-branding rights I mean. See yourself:

iPhone App and Android App Rebranding

BoonEx is developing mobile apps that work with Dolphin. iPhone App and Android App are the first ones to be released. Prime is the only way to get their source-code, modify it, and publish the apps as your own, without see more references to BoonEx.
Desktop App (Adobe AIR) Rebranding

Starting with ver. 7 Dolphin will come packed with an Adobe-AIR based desktop application, which allows your site users to connect and communicate with each other without even opening a browser. Prime customers are the ones to have the right to re-brand the app as their own. Dolphin 6.x comes with a JAVA-based app, and terms are the same.
PrimExtras

Prime customers receive occasional extra modules, templates or services from BoonEx. It can be early access to the new Dolphin components or an extra promotional listing in the BoonEx newsletter, or even extra licenses at no cost. PrimExtras is a new service, and we have huge plans for it.
Featured Listing

The Dolphin-based sites of our Prime customers will receive an extra "featured" listing at BoonEx Sites, which will help you increase your search engine rankings and will lead some extra traffic to your site.