Yes this should be possible with some constraints. If you look at the video he mostly modifies the Object that defines the game mechanism. So if you register a callback in the game that simply call the methods of the game objects then you can simply hot-swap the code that get executed when those methods get called.

If you look carefully some of the code extracts of the first tutorial use jsFIddle to allow the reader to play with the code. This is not as impressive as this demo since you have to manually re-start the game to see your changes but it has the advantage to expose the complete code and not only the OO model.

But this is a very ellegant demonstration and I will think about it for my next tutorials. If you try to do something like this using gameQuery I'll gladly help you with it!