"Wasn't the hack implemented by the group calling themselves the Smoking GNU?"
it was, but the GNU code wasn't the hack. The group took its name from the code used to transmit the names of dead operators because they were inspired to form by the clacks company seemingly not caring about the operators any more.
(Thank you to the second person who upvoted my previous post, by the way - that was my 3000th upvote. :D)