Will Marzipan Apps Be Locked to the Mac App Store?

Dave Mark brought up a good question regarding Jason Snell’s article, which is about how the Mac won’t be locked down like iOS with the introduction of Marzipan apps.
Will I be able to download a Marzipan app from a developer’s site and just run it on my Mac? Or will Marzipan restrict apps to the Mac App Store?
I have a feeling they will be restricted to the MAS. If Mark Gurman is right, Apple plans to merge iPhone, iPad, and Mac apps into a single download. After that, the two App Stores could be merged. Locking Marzipan apps would be the logical first step down that road.