Well, I am glad to say it looks a lot like K-Un was just blowing the normal smoke:
The Chosun Ilbo (English Edition): Daily News from Korea - N.Korea Says Factory Owners Can Come to Kaesong
I still think there is a small chance until the 25th of June (start of the original Korean War) but clearly they have toned down the oversensitive demagoguery, and this opening comes after their delegation to China got back. So, it does seem that China stepped up, and got NK in line.