In a new court filing, Epic Games challenges Apple's position that third-party app stores would compromise the iPhone's security. And it points to Apple's macOS as an example of how the process of "sideloading" apps -- installing apps outside of Apple's own App Store, that is -- doesn't have to be the threat Apple describes it to be. Apple's Mac, explains Epic, doesn't have the same constraints as found in the iPhone operating system, iOS, and yet Apple touts the operating system used in Mac computers, macOS, as secure.

The Cary, N.C.-based Fortnite maker made these points in its latest brief, among several others, related to its ongoing legal battle with Apple over its control of the App Store.

Epic Games wants to earn the right to deliver Fortnite to iPhone users outside the App Store, or at the very least, be able to use its own payment processing system so it can stop paying Apple commissions for the ability to deliver its software to iPhone users.

A California judge ruled last September in the Epic Games v. Apple district court case that Apple did not have a monopoly in the relevant market -- digital mobile gaming transactions. But the court decided Apple could not prohibit developers from adding links for alternative payments inside their apps that pointed to other ways to pay outside of Apple’s own App Store-based monetization system. While Apple largely touted the ruling as a victory, both sides appealed the decision as Epic Games wanted another shot at winning the right to distribute apps via its own games store, and Apple didn't want to allow developers to be able to suggest other ways for their users to pay.

On Wednesday, Epic filed its Appeal Reply and Cross-Appeal Response Brief, following Apple's appeal of the district court's ruling.

The game maker states in the new filing that the lower court was led astry on many points by Apple, and reached the wrong conclusions. Many of its suggestions relate to how the district court interpreted the law. It also newly points to the important allies Epic now has on its side -- Microsoft, the Electronic Frontier Foundation, and the attorneys general of 34 states and the District of Columbia, all of who have filed briefs supporting Epic's case with the U.S. Court of Appeals for the Ninth Circuit.