It has opened around in July 25th, 2015, as the 19th Movie is released in August 5, 2015 throughout Korea.
Sells no merchandise related to DC but gives out small silver badges that assemble the 19th Movie to whoever buying a sandwich set meal in the cafe. (Not sure if the stock has run out yet.) A similar event is run for those who purchase two movie tickets and they will receive the badge but the color is gold instead of silver.
It will remain open until August 25 if my memory isn't wrong.
There's no website link associated I can provide.