... sino un sistema operativo escrito en Java con el kernel Linux por debajo:

The main difference is that most other platforms run in native code and then VM languages bind to that native code (e.g. Python/Java calling out to syscalls, WINAPI functions, etc...) while Android OS actually is written and runs IN Java. As soon as basic Linux kernel is up, Dalvik is started and THEN the rest the OS (UI compositor, audio manager, process/activity manager, SurfaceFlinger, etc.) is loaded as Java classes. Android is basically Java code that calls out to native code for acceleration (like most Python libraries) not the other way around as you're used to from other platforms. Think of Android more like "boot to Java" than a Linux distribution.

Which means there are no native calls to be called - whole Android API is a Java API. So if you want to implement another language or write an app in C, you need to still have a JNI bridge between your language/code and Dalvik which lets you call Android to draw UI on screen, access data about filesystem, system services, schedule service startups, add icon to launcher, show notifications, ... anything really.

(El remarcado en negrita es mío)

:wq