You can get the plugin source by downloading Messenger’'s url=http://www.jivesoftware.org/source.jspsource[/url] as a zip/tar.gz file or via SVN. There is also a basic plugin example in the url=http://www.jivesoftware.org/builds/messenger/docs/latest/documentation/plugi n-dev-guide.htmlPlugin Development Guide[/url].
Somehow, the forum inserts an HTTP encoded space in Ryan’‘s link to the Plugin Development Guide (it happens too when I try to link the page myself - probably has something to do with the length of the url). Remove the %20 from the url and you’'ll be fine.
The guide outlines four integration points - I found those, combined with the javadocs, to be really helpful.