GmsCore
Free implementation of Play Services
...How is that? While the core operating system is still released as part of the Android Open Source Project, the majority of core apps are not. It gets worse: More and more libraries and APIs are only available on phones that run various Google apps pre-installed, effectively locking third-party apps to the Google ecosystem. For these reasons Android is described as being a “look but don’t touch” kind of open. At this point, several popular open-source applications already require some of Google’s proprietary libraries to be installed.