One Friday last August, Tim Sweeney, a billionaire game developer, sent an email to a contact at Microsoft: “You’ll enjoy the upcoming fireworks show.”A week later, Mr. Sweeney’s game Fortnite delivered good news to players on iPhones: They would get a discount on items in the game if they completed the purchases outside Apple’s payment systems.The change violated Apple’s rules and cut the iPhone maker off from collecting a commission on one of the world’s most popular games. Hours later, Apple kicked Fortnite off the App Store.Mr. Sweeney’s company, Epic Games, …
