The least understood area of the Android ecosystem has always been the highly secretive Google Play Apps licensing process. While Android is open source, the Google applications, like the Play Store, Gmail, Google Maps, Google Play Services, and others must be licensed. This licensing agreement is called the “Mobile Application Distribution Agreement” (MADA) and comes with tons of restrictions. Previously, MADA details have come out of the Skyhook case, but those agreements were from 2009, a time when Android was only at version 1.1. Thanks to the still ongoing Oracle v. Google trial, a “new” version of the Google App licensing agreement has been made public.
Don’t forget the patent licensing fees Android handset makers pay to Microsoft.