Quoted from PinMonk:Another change from the book that messed up the story was that Morrow GAVE Wade the quarter that would be key to him winning the game in the movie. Essentially, he directly helped Wade cheat. In the book, Wade found a PacMan in the museum and EARNED the quarter, with no help. In the framework of the story, Halliday would not have condoned cheating.
He didn't cheat, he won a bet.