I'm reading the forums here:
http://www.outlinersoftware.com/topics/tlist/608
(nice resource)
Looks like lots of companies making outliners are going out of business (e.g., Ultrarecall), partly because Microsoft entered the scene with oneNote and pretty much outclassed everyone (!). Others reacted by increasing prices (e.g., surfulater) or cutting them down (TexNotes)... There are some interesting developments (zoot coming back with version 6, connectedText, etc) but things look bad.
This is a pity. There is lots of talent in this subclass, I'd hate to see innovation die.
Under linux, the situation is even worse. Nothing comes close to a working solution for me. This sentiment is echoed in those forums. So after spending 2 days seaching for substitutes, I'm sticking with onenote and forgoing the possibility of something portable and open. If it's difficult to surviving in the (commercial) windows world, chances of a strong linux app are smaller even. BasKet had no main developer for more than a year, and just recently picked up speed (still, light years behind onenote, and several design decisions make it not useful for me, e.g. one has to click to start a note, no tab indentation etc).