Seems the new viewer will not be open source - only SnowGlobe will be that, and as of yet we do not know how much SnowGlobe 2.0 will differ from Viewer 2.0.
Anyway, seems that the Lab is now tightening its grip on the viewer marked, perhaps in an effort to take back control of the development of the viewer. 3-rd party viewers like Emerald has become popular with new features not supported in the official viewers, and some of them, like the new attachment points means that users of the official viewer may see less of an avatar than users of Emerald. Having external project making these kinds of architecture decisions if of coerce unacceptable for the lab.
And where is the Statistics bar? Have they removed it from the viewer, making it an "advanced SnowGlobe user option" only? hmmm that I don't like.