On the new EyeX Engine 1.8.0 (released a couple of hours ago: http://developer.tobii.com/tobii-eyex-2-0/), that key hooking has been removed altogether. We now encourage people to use their own context dependent key hooking or secondary input hooking instead. The EyeX SDK 1.6 have updated samples that show how to do this.
(And yeah, it was because there are so many different keyboard layouts out there that it was possible to select another key in the EyeX Settings).