> dbus-java exists, does that magically turn dbus into being primarily implemented in Java?

it does if the only other implementation is basically the JNI native methods of dbus-java. This is what libbinder_ndk looks like from the outside. If there's a newer libbinder that does not look like a Java mess , I have not yet seen it.

Not negating that it may exist; the libbinder you quoted above looks similar to openbinder but I have never used it.