Well this is a very good question. It depends on how you want to say it. And that has been the problem in the calendaring industry from day one. The way dotCal sees it is this. Publishing means one way... out bound from the source. That can mean that someone is subscriing to your calendar changes or they view it through an "Embedded Business Calendar" widget on one of our business customers web sites.
Sharing can be one-way ... but we think Sharing means two-ways and in our world that measn CalDav, 2 way sync, or true calendar sharing.
So bqck to the question, how are Publishing and Sharing differnt, we think Publishing is a good term for one-way and Sharing is a good term for a controlled two-way sync on . Please feel free to chime in on this one. (:-)