Academics from a wide range of fields are at least generally familiar with Creative Commons licensing. In contrast, Copyleft licensing seems to be less widely known despite its history as the precursor to Creative Commons licensing.
Copyleft licensing originated in the 1970’s specifically in the area of software development. Software developer Richard Stallman is credited with creating Copyleft licensing as it is used today. Detailed information about Copyleft is available at the GNU Project web site (http://www.gnu.org/copyleft/) which is sponsored by the Free Software Foundation.
A Copyleft license is just that – a license. Developing and releasing software under a Copyleft license does not place the work in the public domain. The copyright remains in tact. However, the terms of the license give users broad rights and typically free access to the software including its underlying code. Users are then allowed to copy the software, use it, modify it, and distribute their modified version of it (in copyright lingo, the modified versions are derivative works). When distributed, these derivative works must be made available to others under these same terms.
Given the broad rights available to users of Copyleft licensed software, some might wonder why developers use it instead of simply releasing the software as a public domain work. The answer to this question lies in the underlying philosophy of Copyleft. The entire point of Copyleft is to prevent someone else down the road from developing a derivative work and turning it into a proprietary commercial product. A work that is placed in the public domain can end up being used in this way. The same is not true under Copyleft. Under Copyleft, distribution must be made under the same terms. Certainly, a software developer might modify Copyleft software and tie up that particular modification by never sharing it with anyone else. Copyleft can’t prevent that. But all such a developer has accomplished is creating a derivation that only he or she can use.
While the word copyright is a legal term of art, the word copyleft has no legal significance. According to the GNU Project web site, it is a sort of word play on the term copyright in that “left” is the opposite of “right.” Similarly, the symbol associated with Copyleft plays on the commonly known copyright symbol which is a ‘c’ enclosed in a circle. In contrast, the Copyleft symbol uses a reversed ‘c’ inside a circle.
The Linux operating system is one of the most widely known and successful software products developed and distributed under Copyleft. Wikipedia is another example of a project that continues to flourish under Copyleft.
The impact of the philosophy underlying Copyleft is clearly visible in the later development of Creative Commons licenses. Creative Commons licenses continue to gain in acceptance and use in educational applications such as course materials. In the end, both share a commitment to ensuring reasonably easy to use and access copyright information and licensing agreements geared to those seeking to advance their fields by sharing their creative undertakings in ways that encourages collaboration and innovation.