The settings given by Google for Android
"Android is an open-source software stack for a wide range of mobile devices and a corresponding open-source project led by Google. "
"Android is an operating system based on the Linux kernel with a user interface based on direct manipulation, designed primarily for touchscreen mobile devices such as smartphones and tablet computers [...] "
left me in doubt about the platform's goals.
Perhaps a response that explains the difference between SO and software stack will bring to the reader an understanding of these two concepts.