While DZone was at JavaOne 2015 this week, Azul Systems released an early access version of Zulu, which is a certified OpenJDK build / JVM, that supports the latest JDK 9 features. You may know them well by now:
REPL and JShell
Enhanced graphics performance
This news also marks the unveiling of zulu.org, a sharp-looking community site for Java developers that are interested in highly-optimized JVM performance. Via the press release, we also know that Azul "will provide regular updates to pre-release versions of Zulu 9 based on the development cadence of the OpenJDK Java 9 project."
So yes, Java 9 is still very young and in flux, but Azul made the call to give developers access to the fresh features now even though they'll have to put in the work to keep it up to date all the way to September 16, 2016.