That's the embed, which actually works well for chatting as you use the forum. At the end of every post or thread you read, there it is waiting for input. It will open in a window if you click the upper right icon or "launch a window" text.
It does things that aren't obvious like informing you of private messages, and linking usernames to profiles for anonymous users, but "send a private message" if logged in. They even embed it in static HTML pages.
