I am very glad that Urbit exists and is being funded. I have corresponded with the author and differ with him on some design decisions that I consider significant. Nonetheless, it is an excellent example of the "rethink everything" type of ambition that I would like to see expressed more.
Quote from their tutorial: Whipping or clamming on a %weed simply ignores the sample and reproduces the example - as does bunting, of course. However, %weed remains quite useful. Clearly free thinking people.
http://www.urbit.org/