[gebna]

Google made money on Android. As long as you're not making direct changes to Kernel code, you're free to close source anything you add. The existence of AOSP didn't prevent the Playstore or google play service from making Google the sole controller of Android. That's how it turns into a goldmine.

[TheLoafOfBread]

Android is kind of pointless without phones it is running on, so having a code does not mean you have any use for it. Same for routers using Linux. Kind of pointless to have source code when you don't have the hardware.