I'm not sure to be honest. The actual JRE based on OpenJDK has additions to the code according to http://openjdk.java.net. I couldn't find anything called 'Java' that wasn't this code.
The OpenJDK FAQ is of course 404ing. Thanks Oracle.
Remember this only applies to the F# compiler and not to the .Net runtime which you need to run the compiled code. Microsoft is friendly with Mono currently, but so was Sun with Android.
Only OpenJDK is open source. Other than that, Java is closed -- and to certify a Java implementation, you have to pay a license fee, which not the case for .NET.
IMO were it not for the Oracle acquisition, it would be a matter of time until Java were fully open sourced, but with Oracle in charge now I suspect that it's not going to happen.
Java is closed for commercial use under the terms of the GNU - did anyone notice how the press picked up on the story then it completely vanished from the news? ...guessing a gag order was issued
I don't think that's correct. AFAIK there's no certified OSS Java. And if it isn't certified, it can't be called Java.
It would be correct to say there's Open Source 'Java compatible' environments.