The hosts of a VICE documentary were able to visit a computer lab [1] last year, and looking at the start button(?), it looks like an older version of Red Star OS.
According to the CCC talk by a guy who went there to teach CS, most everyone uses WinXP - Red Star is used in industrial setting mostly.
If that's the case wonder why they went all the way to so meticulously clone OS X UI.
Perhaps the reason is similar to the (apocryphal) tale of how the Tu-4 was manufactured with bullet holes copied from a captured, battle-damaged B-29 because Stalin said to copy it exactly.
That or they're planning to transition from XP to Red Star for everyone whenever it's 'ready' - which would be quite an ambitious plan!