Last Saturday Matthias Klose announced on the ubuntu-devel-announce mailing list the official certification from Sun of the OpenJDK 6 on Ubuntu 9.04. This seems to me a very important step for anyone developping and deploying Java on Ubuntu, and as there seem quite a bit of this happening on our server platform, I thought it was worth giving this announce a bit more visibility.
The Technology Compatibility Kit (TCK) for Java is a very throrough test suite made to insure that each of the components shipped on a given OS respect the Java specifications. Validation of the test suite by Sun is what provides the certification. Achieving this provide a great level of assurance to anyone willing to deploy its application in a new environment and allows validation that the Java specs are not derived by vendors to lock-in their customers, which has been tried in the past.