Nowadays, a decade later, the crafting recipes are available within the game itself, and the "small studio" was sold by Notch to Microsoft.
That doesn't detract from the author's argument though - a game is not its code, assets, the devs' design "intention" (whatever it means), or even its set of rules; it's what players do with those things. And in the case of Minecraft this is shown by the shared experiences and knowledge of the players, and its success as a game is that players can do a lot with it.