Developers are building new software for apps that lets companies bill customers without paying Apple ($AAPL@US). Apple currently takes up to 30% of app sales. Developers are preparing for new changes Apple has to implement after a federal judge ruled in September that Apple has to let app developers link to alternate payment systems. The ruling came as a result of a legal battle between Apple and Epic Games, the maker of Fortnite. The App Store is a part of Apple’s services business, which reported $53.8 billion in sales during fiscal 2020 at a 66% gross margin, accounting for about 20% of Apple’s revenues. Developers are preparing several options since it’s unclear what they’ll have to do to abide by Apple’s new rules. The order takes effect on December 7.