Eldritch challenges USA congress's recent retroactive extension of the term of copyright by another twenty years. Many of our most important programs do not come with full manuals. When people exercise their right to modify the software, and add or change its features, if they are conscientious they will change the manual too-so they can provide accurate and usable documentation with the modified program. O'Reilly books are mentioned in the article as examples of books that would be much more useful if distributed under copyleft. Tim O'Reilly, CEO of O'Reilly, disagrees The debate about free texts is also vivid on the area of texts published on the web.
Many sites publish under close to copyleft licenses.
You can read the OR Magazine License . Check out also the rationale which includes links to other licenses used to distribute documents in the web today. The FSF maintains links to documents related with free music, free texts, use of copyleft in non-software materials, etc.