Details on Aftermix have been slowly emerging, and Anthropomedia points to two of them in a post on Brightcove's Aftermix. For the MediaPost video mentioned, go to the 35 minute point to see Jeremy Allaire's demo of Aftermix. Or you can check out the early support video.
I can't comment on the blog post's questions on the underlying business model, but I can briefly comment on the blog post's suggestion that Aftermix is half-baked right now. We have a team here that includes people who previously worked on Flex, which is the development technology for Aftermix. This Flex group includes me, and you can also see that I went to Brightcove seven months ago. Hopefully I've been doing something since then. :) I wish I could say more, but that's for another day. In time, on this blog, you'll hear more about the fully-baked version.
As for the version of Aftermix shown in the videos, a lot has changed (and is better) in our local builds. To let out one detail, the tab navigator is gone. Those of us who have seen too many Flex applications that look alike will appreciate this.