Are Android apps open source?

Android is open-source , but most of the software we run on top of the platform isn’t. This is true whether you get a Pixel device or something from Samsung. Unlike in the early days of Android, the Pixel Launcher and most of Google’s apps have become closed-source.

It’s free opensource software , but Google releases only EULA (hence non-free) builds.17 May 2017

You are of course free to develop applications for other platforms, including non-compatible implementations of Android , provided that this SDK is not used for that purpose.