By the usual definition of MOOC, you have permission to copy any material, although the permission who gives you permission may not actually have that right. E.g. the instructor could make available protected material that they cannot grant permission to copy. However, they can grant permission to copy the stuff that they create – the stuff that they write on the blackboard, for example. By writing the material down, it has the fixed form that entitles it to copyright protection. But you really need to look at the license that is granted to you to see just how "open" the course is. For example, rewording is creating derivative material, and you may not have permission to create derivative works. In a non-trivial number of course that I've seen, the instructor fails to include a license statement.