You can grab the new client library here:
http://wave-robot-java-client.googlecode.com/files/wave-robot-api-v2.zip
You can read about the changes in the changelog wave:
http://code.google.com/p/google-wave-resources/wiki/RobotJavaClientLibraryChangelog
You can also choose to 'Follow' that changelog wave from the client,
for real-time updates on future changelogs:
https://wave.google.com/wave/#minimized:search:in%253AInbox,restored:wave:googlewave.com!w%252B3djWsKA4A.1