In context: Until recently, Apple required third-party iPhone and iPad developers to conduct in-app transactions through its internal payment system. However, litigation has changed this landscape, and now the company must allow external payment methods. Developers have started updating their apps to offer alternative payment platforms when available.

Amazon has released an update for its Kindle app on iOS, adding a new "Get Book" button that directs users to purchase eBooks directly from the Kindle store. The e-commerce giant made this significant change following a recent court ruling against Apple, which forced Cupertino to open its mobile ecosystem to external payment options.

Amazon told The Verge that it continuously improves its apps to enhance the user experience. With the new "Get Book" option, eBook readers can now complete purchases through their preferred mobile web browser. While the process still requires some steps, it makes the iOS Kindle app more functional than before.

Previously, Kindle customers had to leave the app, search for their desired eBook on Amazon's website, complete the purchase, and then return to the app to sync the book. The new "Get Book" option still sends users outside the Kindle app to finish the transaction, but it's a tighter integration.

After losing its legal battle with Epic Games, Apple revised its guidelines to permit third-party payment options in iOS apps. Spotify quickly took advantage by rolling out a payment service, and Amazon is now doing the same – though the change currently applies only to iOS users in the United States.

The court's decision seemingly hobbles the so-called Apple Tax – the 30 percent cut Apple takes from App Store and in-app purchases. However, it is still firmly in place for paid apps in the App Store and for developers choosing to use Cupertino's payment platform. Meanwhile, Apple has appealed the decision so a higher court could reverse the decision. Despite mounting scrutiny, Cupertino continues the fight to reinforce its tightly controlled ecosystem.

Lawmakers may eventually force Apple to loosen its grip on the mobile app marketplace. A newly introduced Congressional bill – the App Store Freedom Act – aims to compel platform holders like Apple and Google to allow third-party app stores and sideloading by default rather than blocking them at the system level.