Thanks for the excellent analysis of the "deal."
(But you've overlooked my real question...whether developers can go in both directions, i.e. sell their apps through the Mac App Store and independently?)
Yep, they sure can. There's nothing in the Apple Store Ts & Cs that prohibit that at all, and in fact quite a few developers do do this.
I can understand why many developers, especially smaller developers, would choose not to, for the reasons I list above. I reckon it's very tempting, once you're in the Apple App store, to just want to go hands-off and let Apple send you a check every month. And the App Store is large enough that even after Apple's 30% cut, that check might still be bigger than what you could do on your own.
That's actually a danger I see in the App Store model, to be honest. Not that Apple will come in and take over Mac app sales by imposing draconian terms on developers or forcing people to stop selling through other channels, but simply that they will make it so easy and convenient to use the App Store that a lot of developers will simply decide they don't want the hassle of selling software on their own.
That might create a situation where Apple, without aggressively trying to force developers to use the App Store, will end up with
de facto control over Mac software sales anyway. As more and more apps appear on the App Store, it gets more and more traffic. That makes it more and more attractive to other developers, who may choose to put their apps onto the App Store simply for the exposure, and once there may decide that it isn't worth the bother to try to maintain their own Web sites or distribution channels.
There will always be some developers who don't go the App Store route, and there will always be developers who do both, but I think the App Store model may become so attractive to developers that it starts strangling off other software distribution channels without having (or needing!) any rules or prohibitions against developers selling their apps outside of it.
