I've spendt most of my morning looking at this.
Use manycam to stream the desctop and an adobe server to uploade it. manycam is a vitrual webcam program so you can have multiple webcams effects or desctop feeds from it. feed goes to justin.tv
Use vlc to upload the feed to justin.tv
manycam and the server took much of the computer and the feed were ok
vlc took much too and the feed was crappy
I might feed somethings but if things get complicated like the tarrein in bttf jumps then the feed will look bad.