The title of this thread includes "Hop-Proof". While I expect that is really just hyperbole, I wondered what it would mean to be "Hop Proof"? Contracts with the pool members to never use another pool? Kind of like getting married?

You're correct. There really is no such thing as a hop-proof pool. As long as you control your hardware, you can point it anywhere you want to mine. PPLNS pools in general discourage hopping, but they certainly don't prevent it.