I I'm not mistaken, the Android OS or even China Alibaba own mobile OS Aliyun maybe using Linux as the base to build their "new" OS. Since Linux has gone through so many iterations, most major problems like stability,scalability etc should be ironed out, then take this OS and build your own proprietary extensions on it in a much short time-frame to market delivery.
For this, we really should thank Linus Torvalds for creating such a wonderful OS called Linux and his belief in Open Source which ultimately spur the OS to much greater heights than those commercial proprietary ones :P