Just got curious. If Android is based on a modified Linux Kernel and its source code is closed, doesn't it violate the terms of GPL2, that GPL-derivatives must also  supply their source code, Liberty or Death? :)
Does Android break GPL?
android;gnu;gpl
Android's source code is released by Google under open source licenses, although most Android devices ultimately ship with a combination of open source and proprietary software, including proprietary software developed and licensed by Google. Open source part (http://source.android.com/) is licensed under Apache Software License, Version 2.0 (Apache 2.0), but with exceptions, for example, the Linux kernel patches are under the GPLv2 license and Google does not violate it.While Google is following the letter of the GPL and LGPL licenses for code it is using in Android, other vendors that are using Android and are presumably modifying that kernel code are not compliant with these licenses. 