Yes. They are currently releasing new builds of MC12 to the "general public" about once per week. Occasionally more or less often, if the current "beta" builds are more or less stable (respectively). To be clear, JRiver has made no specific promises of targets for releasing new builds, but based on how it's been working thus far, they've been updated about once per week.
That gives those of us who download and test the new builds daily a chance to weed out any bugs and beat on the builds for a while, before they go out to the world-at-large. That allows JRiver's programmers to take more risks with the software (without worrying about alienating new, inexperienced, or frankly normal customers who just want their software to work), by limiting the really "bleeding edge" builds to a smaller closed group of experienced (and willing) users. As soon as the new stuff has proved "mostly safe", then it is generally pushed out to the public.
It's a little similar to the "trunk vs. branch build" system that Mozilla uses for their releases (though they have a more free form three tiered system -- unsurprising for an open source project).
