So it immediately raises the question why isn't this released?
The reasons I can think of are:
* Performance isn't what they want yet.
* Implementation isn't what they want yet.
* There are security issues they still need to fix.
OR putting on my tin foil hat for a second:
* Apple sees WebGL as a possible threat to their app revenues as a soild WebGL implementation could allow developers to avoid entering their app market place and instead charge users directly. It would also allow developers to deploy to other platforms with the same code base.
Obviously the last point is a bit nutty but one can't help but wonder if it is a consideration.