[Callers] Choreography and Copyright

The folk community is generally very open on sharing ideas and choreography. I suspect few of us would think twice about calling a dance that we found when someone else called it at an event. As for publishing it on the internet, we'd probably be more reticent, especially if the author has not published it, or has done so in booklets that are sold. This is generally the opposite of what happens in other dance communities, where the creation is jealously guarded. This made me wonder whether we are too lax in assuming that a choreographer is happy for us to make full use of their work. So my question on the subject of copyright of choreography is: Under what circumstances do we have the moral and/or legal right to: 1) Call a dance written by someone else? 2) Publish a dance written by someone else? 3) Modify, or borrow from, a dance written by someone else? Jeremy