This is definitely fake - why would anyone who stumbled across a way to cheat a gambling site post how they did it on youtube? That would only bring the attention of the site owner who would then close the loophole and 'ruin' the exploit - in turn costing the person who discovered it the future profit they could have gained by quietly cheating without raising any attention to themselves.

The instruction document linked in the video also has a dead giveaway that it's fake - it states that you need to withdraw your winnings without refreshing or reloading the page (which would cause the script to stop running). Once the funds were won and in your account, what would it matter if you were to refresh the page before cashing out? My guess is that the script will end up recording your password so that they can later drain your account.