“Epic Games, the developer of Fortnite and the widely used game-making software Unreal Engine, is about to start selling other companies’ games, too.”
https://www.theverge.com/2018/12/4/18124203/epic-games-fortnite-valve-steam-game-store-distribution-unreal-engine
Epic game is launching a new online store similiar to Steam, even becoming a threat to Steam’s dominant position as the lead distributor of PC titles,
The Epic’s store plans to launch soon, and with various number of PC and Mac games and open up to more developers.
Before Fortnite launched, Epic developped its own launcher for its own game, like Blizzard EA and Ubisoft.