While this is very interesting, instead of working with just a few partners, Microsoft should’ve just opened the code for their new rendering engine altogether. At this point, it makes little sense to keep this kind of important code closed.
When it comes to open source, the new Microsoft is only a little bit new.
Like with Windows, I’ve heard it said they have too much licensed code to be able to open it up fully. IRIC, OS/2 had the same problem.