[follower]

To me "notify" signifies a "one off" email saying "hey, we're live".

I think the "click here to continue to be on the list" is more polite than "click here to unsubscribe" in this case.

What would be better still would be to spell out the situation under the input box. e.g. "We'll only send you one email when we're live" or "We'll spam you everyday until you tell your friends" or something in between. Just be upfront about it so people's expectations are accurate.