If you own a Kindle, you’ve experienced the power of having a Digital Locker and the ability to download your purchased content to just about any device. The notion of “buy once, read anywhere” will now also apply to your Android apps purchased through the Amazon Appstore.
Customers who purchase an app will retain an entitlement to their app even if they decide to replace their current Android device and/or purchase new devices, as long as the new devices meet the installation requirements of the app. This provides insurance to customers that their purchased apps will be available for use on all supported devices, even if the customer has uninstalled or otherwise removed those apps in the past.
The digital locker service combined with a robust Digital Rights Management (DRM) solution not only make managing apps easier for customers, they also address one of the biggest concerns developers have: unauthorized copying and distribution. An authorized user can now install your app on any of their supported devices; however, if you chose to apply DRM on your app at submission time, your app will not run on unauthorized devices.
Any app that has Amazon DRM applied to it will require users to have installed and signed-in to the Amazon Appstore client to access the app. When an app is accessed by the user, it will verify with the Amazon Appstore device service as to whether the user has an entitlement to the app. If the user does not sign in or does not have an entitlement to that app, then the app will not be usable. However, any user can gain an entitlement by purchasing the app through Amazon.
To find out more about the Amazon Appstore Developer Program, go here