first of all: I don't know more about this whole issue than you do; in fact, this thread was the first I saw about the new Flash revenue model. 😉
I've now read carefully through all articles I could find, and it seems to me that Starling is *NOT* affected by this change at all. Starling does not use domain memory (again, something I had not even know exists), so it's not affected.
I think you can summarize it like this:
When you use Adobe Alchemy (to call C/C++ code from AS3) in the browser plugin (not AIR) AND use stage3D in the same project, you will have to pay a fee to Adobe once your revenue exceeds 50k USD.
In other words, I think this whole model is targeted at professional 3D engines like Unity. It allows vendors of such engines to target the Flash Player plugin -- and that's who Adobe wants to get revenue from. Which is an understandable and acceptable step, IMHO.
I will try to find out if my assumption given above is correct, and will report back here if I know more.
(And I might add a small *sigh* to question Adobe's apparent inability to announce information like this in a concise and clear way. This whole affair reminds me of the announcement dropping the *mobile* Flash Player plugin just a few months ago.)