I didn’t know anything about copyleft. I didn’t even know such a word ever existed—at all—until I came across an essay entitled What is Copyleft? published in Free Software, Free Society: Selected Essays of Richard M. Stallman.
And I quote,
Copyleft is a general method for making a program free software and requiring all modified and extended versions of the program to be free software as well.
I know you are all too familiar with copyrighted software or proprietary software. And you are well aware of the limitations it gives us, users—taking away our freedom e.g. to run, modify or redistribute a program—freedom we can only have with free software.
Freedom in Free Software
The word free in free software does not pertain to the price of the software but the freedom that you get with it. With free software,
• You have the freedom to run the program, for any purpose.
• You have the freedom to modify the program to suit your needs. (To make this freedom effective in practice, you must have access to the source code, since making changes in a program without having the source code is exceedingly difficult.)
• You have the freedom to redistribute copies, either gratis or for a fee.
• You have the freedom to distribute modified versions of the program, so that the community can benefit from your improvements.
Making Programs Free Software
One can make a program free by putting it into public domain without placing any copyrights, but still, other users can take away the freedom that comes with it by making the program proprietary whenever they want to.
If you want that freedom is passed perpetually from one user to another, copyleft the program instead.
To copyleft a program, we first state that it is copyrighted; then we add distribution terms, which are a legal instrument that gives everyone the rights to use, modify, and redistribute the program’s code or any program derived from it but only if the distribution terms are unchanged. Thus, the code and the freedoms become legally inseparable.
Essentially, to copyleft a program doesn’t mean that it is not copyrighted. Rather, it is copyrighted in order to make sure that it becomes a free software.
Proprietary software developers use copyright to take away the users’ freedom; we use copyright to guarantee their freedom. That’s why we reverse the name, changing “copyright” into “copyleft.”
If you want to learn more about copyleft and free software and the underlying philosophy underlying of the free software movement, I suggest you download this e-book, Free Software, Free Society: Selected Essays of Richard M. Stallman.
It has a total of 230 pages (including the cover, table of contents, license statments, etc.) with 4 sections and 21 essays.
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