It is de-facto Java.
It uses java syntax, java libraries.
To say it is 'not Java' is borderline disingenuous.
Technically, there are differences which are real, and it's very fair to point them out.
But - Java syntax + java.lang/java.io/java.net/java.reflect/java.util + a vm, can use a JAVA IDE and java build chain, use 3rd party java libs ...
=> it's java.