They own the trademark "Android", and their own proprietary stuff, i.e. Google Mobile Services (GMS), which is Play Store, Hangouts, Gmail, Youtube, Maps, Books, etc. Which here in China does very well without, and companies like Amazon do as well with their FireOS devices. However the OS itself is open source, which effectively means everyone owns it, and can do whatever they like, within the terms of the relevant open source licenses, e.g. MIT, BSD, GPL, etc.
Microsoft owns Windows Phone. Apple owns iOS. But Google does NOT own Android Open Source Project (AOSP).
No matter how many times I explain that it's free as in speech, not free as in beer, I don't succeed do I?
Who proctors Android?
http://www.openhandsetalliance.com/
Google does.
How is the open source defined?
https://source.android.com/
In the AOSP repository.
Who has the git that contains the AOSP repository?
https://source.android.com/source/downloading.html
https://android.googlesource.com/
GOOGLE.
Now you can go there, download it, build on it, branch it and make your own.
But if you find a bug, fix it, and want to return it to the AOSP, what do you think your chances are of doing that with no involvement from Google?
I'll tell you - zero. None. Nada. Zip.
I'm not sure if you're aware of it but every year, there's a gathering. People come from miles away. And at that gathering, people stand on stage, and announce what the new definition of Android is. What features it has, what changes are in store for users and development.
Does everything come from one company?
Mostly but there are significant contributions by the R&D teams by some of the Open Handset Alliance, and even some by private developers.
Is it called Android I/O?
No.
Is it called Everything Is Free In China And Neener Neener Neener You Can't Stop Me We're A Socialist Autocracy I/O?
No. No it is not.
It's called Google I/O - and the only people who appear and speak for Android at the keynote are Google employees.
Everyone does not own open source. It doesn't work that way.
Everyone has a right to obtain the source code for open source. They have the right to modify it for their own purposes. And they're allowed to distribute it so long as they follow the open source licensing.
Which to date, has been cheerfully violated by more than one Chinese phone manufacturer distributing Android outside of China.
But as you're not a software engineer and Google services are evidently hard to come by in China, I've searched for the definition of open source software ownership and found this explains it well enough -
"What does `ownership' mean when property is infinitely reduplicable, highly malleable, and the surrounding culture has neither coercive power relationships nor material scarcity economics?
Actually, in the case of the open-source culture this is an easy question to answer. The owner of a software project is the person who has the exclusive right, recognized by the community at large, todistribute modified versions.
(In discussing `ownership' in this section I will use the singular, as though all projects are owned by some one person. It should be understood, however, that projects may be owned by groups. We shall examine the internal dynamics of such groups later on.)"
You can read more about that at -
http://www.catb.org/esr/writings/homesteading/homesteading/ar01s04.html
And also -
http://oss-watch.ac.uk/resources/iprguide
And you mentioned a number of open source licenses. Several you listed don't apply to Android and you've missed one of the biggest one that does.
So when you say that they "can do whatever they like, within the terms of the relevant open source licenses, e.g. MIT, BSD, GPL, etc." that's true - but you may want to read one or two and then ask yourself -
If something has a legal license, and therefore is a legally protected good or service by definition, then who does the law protect?
It doesn't protect an amorphous concept floating around on the Internet - and it doesn't protect The Peoples Socialist Republic of Android, aka The Unified And Diverse People Of Planet Earth.
It protects the defining stakeholders - the owners.
And just as you can find out about those things, you find out more about what it takes for stakeholders to gain that protection. This is a good place to begin -
https://www.softwarefreedom.org/resources/2008/foss-primer.html
And as other companies have come up, let's ask - are Microsoft and Apple stakeholders in Android?
Oddly enough, despite wishing it dead, yes. Yes they are.
Microsoft makes more annually off of its Android licenses than it does its own Windows Phone. Apple has cross licensing agreements with HTC.
Anyone can stand up tomorrow and say, "Here, let me announce the real Android M, coming soon! I have defined it!"
But unless their name is Google, they're going to be sued into the stone age. And not just over some copyright.
You may download the full Android source right now - I've provided the links.
And that's a lot like free beer.
But it is not free beer - cross one of licenses and you can have the owner's attorneys explain that in court. At least in the free world, anyway.
PS - the entire core of Apple's OS X operating system on your Mac? Open source. To the bone. And yet OS X is owned by Apple. Bet you forgot about that.