By "native" they mean JVM-native (not OS-native). I believe what they really mean is that they use JVM primitives for dispatch, as opposed to building their own using functor objects and reflection-like API (which was the only way to implement MOP pre-InvokeDynamic).

It is a bit misleading as there is still a lot that would have to be be emulated - the JVM does not support open types and the Java is centered around classes, which makes prototype mutation hard to implement efficiently ( InvokeDynamic somewhat helps, but would still impose a performance penalty when the prototype is changed).

See also John Rose's article about species: https://blogs.oracle.com/jrose/entry/larval_objects_in_the_v...

I believe it's in reference to a JVM that compiles to native code, rather than a naive interpreted one (most of which went extinct a decade ago).

Seems like the more ambiguous term here is "lightweight."