Copyleft insures that all derivatives of a free program would remain free. Stallman insists this is not so, the copyleft would only apply to the one program and its derivatives. Recently, Netscape decided to release the program code for Navigator. While they used the copyleft as a model, they were concerned enough about some of these issues to devise a different version. Based on copyright.
Creator licenses others to use, copy, and alter.
Requires those others to pass along copyleft license. When an author wishes to allow others to use freely his work, he may declare it to be in the public domain. In programs, this is often called freeware. If a copyright expires without being extended, the work becomes public domain. Legal remedies would be difficult.