It has been said that "Android is not Linux" and this is largely true as Android, and all the value it provides, is given by the Dalvik JVM. There's no reason you couldn't port Dalvik to Symbian, WinMo, iPhone OS, etc.

As such, Android's use of the Linux kernel is purely incidental. It provides no libraries or utilities commonly found on Linux systems beyond Busybox. The only way to get access to the Linux based subsystem is via the NDK, use of which Google discourages as there is no guarantee your software will run on all Android devices (not that there's any guarantee now, but still.)