Answered By: Darren Jeffery
Last Updated: Nov 28, 2017     Views: 48

There are a variety of reasons that make it hard to copy these materials. Some scripts and audio were donated for study only, with a specification that no copying would be allowed. Other materials fall under not only copyright, but also under licensing laws. The University of North Carolina has a diagram of when materials enter the Public Domain at http://www.unc.edu/~unclng/public-d.htm