Indeed, but the situation has changed now. Sun, just before it got acquired by Oracle, had open sourced the last remaining puzzle: the Java compatibility test suite. Which allows anyone to run the test suite, claim and validate that their software is conformant with Java.
Not quite. You have to have your code "substantially based" upon OpenJDK, and be GPLed, in order to use their validation suite. So Harmony still would not be able to use their validation suite.
