KGS sound partially works for me on OpenJDK 7 (and Pulseaudio), without the need for any wrapper or proxy hacks:
Pass sound and chat notification sound work.
Stone clacking and voice transmission does not work.

Maybe at least stone clacking could be changed to use the same means for sound generation as chat/pass do?

It should be noted that Oracle (formerly Sun) Java has been removed from some distributions due to the way Oracle decided to handle Java after it took over, so it becomes that more important to support OpenJDK now.

All true. I'd rather use openjdk, but I always end up installing the Sun/Oracle version.

Actually, starting with version 7, the official Oracle JDK and the OpenJDK are nearly identical, and the differences are expected to disappear soon...

(See for example http://blogs.oracle.com/henrik/entry/moving_to_openjdk_as_the.)

I would be very surprised if you still found something that works with the latest Oracle JDK 7 and not with the latest OpenJDK 7 (version 6 is a different story ).

I'm not sure it's an OpenJDK issue. I have the same problem with Debian 6.03 using the sun-java6-jdk package, however the issue is intermittent. Pre-pending "padsp" to the "javaws" command seems to help. Sometimes I have to bring up KGS with "padsp javaws cgoban.jnlp", kill pulseaudio, and restart it before the sound plays correctly.

I haven't had much time to thoroughly test the issue, but I believe it has more to do with pulseaudio than Java. You can duplicate the issue using the Java Sound Demo app.

I had a similar issue but with the sun jdk (solution here).
It turned out, weirdly, that the issue was with the alsa driver. Renaming that driver so that it isn't loaded helped and everything has since worked like a charm with padsp infront of the java command.