I believe this was the default but was changed recently.
When you open Outplayed during a game session, it opens as an in-game overlay, not as a seperate application.
This is irksome as it requires you to be tabbed in while reviewing older VODs, and the VODS themselves become extremely choppy FPS wise.
Additionally, if you have Outplayed open as a seperate application, it closes automatically once you join a game.
Similar thread: https://www.reddit.com/r/Overwolf/comments/1rhl5d0/overlay_opening_in_game
Cheers!