What is Copyleft?

Copyleft is a strategy of utilizing copyright law to pursue the policy goal of fostering and encouraging the equal and inalienable right to copy, share, modify and improve creative works of authorship. Copyleft (as a general term) describes any method that utilizes the copyright system to achieve the aforementioned goal. Copyleft as a concept is usually implemented in the details of a specific copyright license, such as the GNU General Public License (GPL) and the Creative Commons Attribution Share Alike License. Copyright holders of creative work can unilaterally implement these licenses for their own works to build communities that collaboratively share and improve those copylefted creative works.

What is is a collaborative project to create and disseminate useful information, tutorial material, and new policy ideas regarding all forms of copyleft licensing.

This site itself is licensed under a copyleft license, and has received contributions from experts around the world. Thus, is the premier "meta-project" of copyleft: it's useful copylefted information all about copyleft itself!

The Copyleft Guide and Tutorial

The primary project currently on this site is a tutorial book entitled Copyleft and the GNU General Public License: A Comprehensive Tutorial and Guide. This guide describes the policy motivations for copyleft, presents a detailed analysis of the text of various copyleft licenses, and gives examples and case studies of copyleft compliance situations.

Getting Involved

There are various ways to get involved with this project. The primary website is a wiki, and we welcome helpful edits and additions.

For the aforementioned guide and tutorial about GPL and other copyleft concepts, we seek help in the following ways:

Proposing Improvements to the Guide

Pull requests on's Kallithea site to the Guide are most welcome. If you're looking for something to fix, just grep the *.tex files for "FIXME" and you'll find plenty. Many of them are simple and easy to do. Some of them are writing, and some of them are formatting-related.

Joining Mailing Lists

IRC Discussion

The IRC channel is #copyleft on The IRC logs are public here on this site.

Who Contributes to

This site is a joint project of Software Freedom Conservancy and the Free Software Foundation. The editor-in-chief of the guide is Bradley M. Kuhn. The recent changes page shows who has contributed to the wiki, and you can see the Git commit log on the tutorial to see who has contributed to it, and see the list of users who contribute to this Wiki. may be sponsored by various organizations, and organizations may also republish some, or all, of the output of this project under the terms of the CC BY-SA license. However, contributors' work is their own, and thus the opinions expressed in their contributions, IRC utterances, commit messages, mailing list posts, and/or other fora provided by may not necessarily reflect the views of the contributors' employers and/or organizations sponsoring the project and/or organizations republishing's materials. Generally speaking, unless stated otherwise, please assume that individuals contribute to in their personal capacity.

URLs You Can Memorize! has many easy-to-remember URLs. These are convenience URLs that you can memorize and give to people verbally to point them to the right part of The Guide. (Since the guide is very large, we thought a few easy-to-remember ways to tell people where to look would be helpful.) Here are the primary ones:

As time goes on, we'll add convenience URLs to refer to specific parts of the guide, which makes it easy to refer people to portions of the Guide. Here are a the ones that exist so far:

Offsite Resources

More on "What Is Copyleft?"

Here are a few external resources to read regarding the general concept of copyleft: