See attached patch.. adds 2 new config items in the global settings.

2 additional one-line changes in these diffs:

• JabberPublisherDescriptor.java constructor: changed catch from IMException to
  Exception.. I was getting IllegalArgumentException due to null "host" setting,
  and this caused the whole jabber plugin to fail initialization and not show up
  in Hudson at all.
• global.jelly: removed ${rootURL} from the "base" setting.. in my test
  environment I use server:port/hudson to access hudson (sun java system web
  server 7), but the help items in global settings were getting
  /hudson/hudson/plugin/jabber/*.html, so I removed ${rootURL} and those started
  working.

The rest of the diffs are for the 2 new config settings. When legacySSL
checkbox is checked then JabberIMConnection simply uses "new SSLXMPPConnection"
instead of "new XMPPConnection".. the underlying Smack library already had this
support for legacy SSL, just needed a way to make use of it.
The other new setting is an optional alternate nickname to use in group chats..
if blank, it defaults to the original behavior of using your jabber id.

Thanks for this plugin, hope this patch will be useful!