Yes they did it, the engine which seems to be the best 3D engine for flash platform is now available to users, and freely for non commercial use.

So no open source in there, but it might be interessting to check that new library and test its wonderful exclusive features such as:

- BSP tree, which allows to resolve depth sorting keeping a vector approach, so good resolution and performance.

- Embeded collision system

- Frustum clipping (or viewport one?) which is a feature that Sandy has too and which is extremly important while doing correct 3D immersion.

From the small examples I’ve seen so far, the API is good, similar in some points to Sandy3D one.

Now, up to you to test it more, and make some extra demos to  check its performance capabilites.