This wasn't an off-the-shelf app, this was a custom interface that was made by one of the Essentials/ESU staff specifically for the event, I believe it was hooked up to both the streaming PC and the game server during all of the games and I think that was necessary for it to have the functionality it did. Works similarly to what has been used in CS and Dota etc. but iirc it was original code.
Hope that helps.