Are there any open source forums capable of acting like a widget? ...where the forum display can be loaded as the contents of a division (<div>) in an arbitrary enclosing CMS? (in other words I wish I could find an open source forum I could plug into my CMS).

Most forums expect to be the whole show, with <html><head> and <body> tags. Getting rid of those elements ( so the forum itself could become the contents of an enclosing division ) is tricky, because of information passing in the head (if (a,b,c) { header("location: xyz") }, etc.

Forum widgets seem like the inevitable future. But I haven't been able to find any yet. Ah. And I don't want to use an I frame. Thank you.