In a decision that could threaten Apple’s biggest moneymaker, a legal ruling Friday is forcing the company to loosen its grip on its app store.

The federal court ruling settles an antirust case brought by Epic Games, best known as the maker of the popular video game, Fortnite. The case looked at the commissions of up to 30 percent of Apple charges on digital transactions. Epic Games called the commission a price gouging tactic that wouldn’t even be possible if other stores could offer iPhone apps.

The court ordered an injunction requiring Apple to allow iPhone app developers to offer other payment options. The ruling puts a wrap on a trial that actually ended three months ago. Since then, Apple has taken two steps to loosen some of its app store rules. One step was taken to settle a lawsuit, the other was to appease Japanese regulators without adjusting its commissions. Both make it easier for app developers to get users to pay for digital transactions in ways that avoid commissions.

In its Friday ruling, the court ordered Apple to go even further by allowing links and buttons for non-Apple payment options directly within apps. Although it’s a move Apple has steadfastly resisted in the past, it is not clear whether or not the company will appeal the injunction.

While Friday’s ruling included one win for Epic Games, it also handed the company a series of big losses. First, the court upheld Apple’s right to block other stores from offering apps for its iPhone. The court also said Apple was not operating an illegal monopoly, as Epic had claimed.

“As the Court recognized ‘success is not illegal,” Apple said in a statement. “Apple faces rigorous competition in every segment in which we do business, and we believe customers and developers choose us because our products and services are the best in the world.”

Epic C.E.O. Tim Sweeney denounced the ruling in a tweet, writing that it “isn’t a win for developers or for consumers.” He said Fortnite will return to Apple’s app store once it can offer competitive in-app payments. “We will fight on,” he added in a subsequent tweet.