Z:gnu-www-ja-thegnuproject--6dc0e3-The central idea of copyleft i/en

The central idea of copyleft is that we give everyone permission to run the program, copy the program, modify the program, and distribute modified versions&mdash;but not permission to add restrictions of their own. Thus, the crucial freedoms that define &ldquo;free software&rdquo; are guaranteed to everyone who has a copy; they become inalienable rights.