What does "to the public" mean in this instance? Are they going to an open source patent pool or something?
All patents are "open for public access" [1]. And once they age past their "expiration date" (currently twenty years from earliest date of filing) they become "public property".
What Sable is doing is giving up the ability to restrict others based on the patents content's before those patents would normally have expired anyway. So in effect they are having the patents "expire early" -- which makes the contents of each become "public property".