Copyleft Licenses

Some articles on copyleft, license:

Copyleft - History
... An early example of copyleft was the Tiny BASIC project started in the newsletter of the People's Computer Company in 1975 ... The listing began with the usual title, author's name and date but it also had "@COPYLEFT ALL WRONGS RESERVED" ... Roger added his name and preserved the COPYLEFT Notice ...
Applying Copyleft
... Common practice for using copyleft is to codify the copying terms for a work with a license ... Any such license typically gives each person possessing a copy of the work the same freedoms as the author, including (from the Free Software Definition) Freedom 0 – the freedom to use the work, Freedom 1 – the ... In order for the work to be truly copyleft, the license has to ensure that the author of a derived work can only distribute such works under the same or equivalent license ...