UE4 Blueprint Multiplayer Online and Steam

I have a question about the UE4 Blueprint Multiplayer Online game tutorial. I want players to connect and play my game through Steam online. Is it necessary that they have UE4 installed on their computer? Do they also need the game/UE4 project folder on their hard drive in order to play the game?

All the players need the same build of the game and if it is an Editor build they also need the UE4 Engine/Editor installed.