Gamejacker
One who attempts to hijack a game by creating seemingly canon information for it without consent from the author of said game.
Followers of Jadusable's ARG mostly see MHFTT on YouTube as a gamejacker.
Gamejack
A website that pretends to be associated with an online ARG (alternate reality game), but is generally spam. These fake websites cause confusion, promote mis-information, and ultimately waste the time of everyone involved.
That website is not related to the ARG, it is a Gamejack.