The "Active Superko" rule is a particular superko rule which, in combination with permitted self-capture, formally allows play at any empty intersection:
A player who plays the same turn in the same position again he did already before, wins the game immediately.
Note: Although a "turn" usually changes the board position, it doesn't have to.
Among the known superko rules this probably is the least restrictive one, with most surprising results.
Because active superko is applied to turns rather than moves, a player can also win by passing again in a situation he has already passed in before.
(examples will follow)
Where is this rule used???
I don't know.