"... His isn't an online outliner though is it? ..."

No.

  My main app only runs on Windows 
  and Mac. Can't do it with Linux. 
  Shame, I know. [1]

there was a comment on why Winer recently purchased a Eee100 with MS Windows and the answer was because his tools are Win/Mac. The point I was making is Outliners have a long history, Winer was there early. The specification is more important than the tool ~ http://docs.opml.org/

[1] http://friendfeed.com/e/fff3a72d-e91d-eae5-5a82-d5a8fc0c8996