Apple has updated its App Store policies to spell out how developers can link to outside payment platforms, as reported by 9to5Mac. Developers will still owe Apple a cut if they use an outside payment platform. Apple will take a 27 percent cut (as opposed to the 30 percent in many cases) or 12 percent if a developer is part of the App Store Small Business Program, according to a support page about external purchase links.

Section 3.1.1(a) of the App Store Review Guidelines lays down more of the new rules for developers who want to link to alternative payment methods, like how they have to apply for an “entitlement” to enable them. Developers also can’t exclusively receive payments from outside Apple’s walled garden; they’ll also have to offer Apple’s in-app purchase system in their apps.

Tim Sweeney, Epic’s founder and CEO, isn’t pleased with Apple’s updates to its policies. He calls the 27 percent fee “anticompetitive,” criticizes Apple’s rules for how the links appear and how they work, and highlighted what he calls the “scare screen” that users will see when they leave an app to go to an external site.

He says that Epic “will contest Apple’s bad-faith compliance plan in District Court.” I’ve replied to Sweeney and emailed Epic’s PR team to try and clarify what that means.

Update January 16th, 7:25PM ET: Added tweet from Tim Sweeney.