Android is an operating system for mobile devices including phones and tablets.Entry of android into the mobile ecosystem changed quite a lot things.Even 5-6 years back,it was unthinkable for nokia to shed symbian in favour of microsoft's os;but android along with i-os achieved this milestone quite easily.
Unfortunately,everything is not as greeny as it should be for android & google.
While creating android,its developers used linux kernel and java runtime based dalvik VM.All the problem is due to use of this dalvik VM & these too raised only after oracle acquired sun and decided to sue google.
The developers reverse engineer the java VM,named it dalvik VM and published it under apache license.The GPL
license, under which Linux and Java fall, requires users to put their
improved code back into the community. No one can uniquely profit from
it. The Apache license that regulates use of Android has no
such requirement. Android and the Apache license are not compatible with
the GPL.Because of adopting apache,android developers need not to put anything back into the upstream community.Its very dangerous for the open-source community.
Even if google does not want to misuse it,some monsters in future might misuse it citing android as an example.So,though i do not like oracle(particularly after its behaviour with libreoffice),my support is with them.Until some information contradicting this comes into my knowledge,my support will remain with them.
Here is a nice article about this in linux-insider.