usually, high positions (or even devs) in companies are offer packages if they leave, under the condition that they do not join a competitor (most of the time direct competitors are even forbidden) and in case they remain in the industry (likely, given his experience) they are also forbidden to release any kind of howto or inner workings. Take this, with a grain of salt, since I don't work for Blizzard, but I do work as a game developer.