Ajax trees and LiveTree note

Hi you all,

I will have to work in an app where it would be interesting to have a
tree view, and with ajax if possible.

I used LiveTree plugin, but it is abandoned, so two things:
1) the author asks in his web if anybody wants to take the project over.
It was pretty good cause you could implement your data in Ruby terms.
2) Do you know any other Rails-related plugins? I mean, I know
Javascript stuff such as the TreeView from Yahoo. But I would like to
use something more Rails/Ruby integrated, for easiness.