I'm going to guess that it was a mis-merge in the App Store codebase and that Lion will be able to run iOS apps (using the MacBook touchpad or Magic Trackpad for multitouch). I mean, Snow Leopard already runs iOS apps pretty much natively if you have the SDK installed.
If it's anything (it's not, but it's fun to pretend), it could be a sign of integration between the Mac and iOS App Stores. Even if one isn't actually being rolled into each other (which I would assume they wouldn't be unless iTunes was redesigned), it could just be saying "this is also available as a Mac app," possibly with a link to the Mac App Store page.
It`s like a bundle; pay once, run everywhere. Cultured Code`s Things for instance could sell such a bundle with a discount.