Facebook can't revoke the API, because the site clearly states in the footer that "Buddy Hack in no way encourages the usage of any Facebook account other than your own." That seems waterproof to me.
In the world of walled gardens like this, there is no rule of law. If they don't like it, they can revoke access.
I was making an irony.
Oh, i didn't realize. Now that you say so, it seems obvious.