1. Create an account on ustream.tv, you’re going to use your credentials to log into their server.
2. Download and install an IRC client.  In this example I’m going to be using pidgin as it’s installed by default in Ubuntu.  Versions for windoze and mac are available here.
3. Open up the app and click on the accounts menu, and click on manage accounts.
   
4. Click on “Add”.
5. For protocol, choose IRC, fill in your username and password (check the “remember password” option), then in the server box, add chat1.ustream.tv.
6. Save these settings and make sure to click “enabled”  next to it in the accounts window.  This will cause pidgin to create the connection to ustream.tv
7. Close the accounts window then click on the “Buddies” menu back on the Buddy list window.  Then click on “join a chat”.
8. In the channel window, type in the name of the room that you are currently in prefixed with a number sign “#”.

Once you do this a new window should pop open and you will be chatting on ustream.tv in your appropriate room without the hassle of their java web client.