Copyleft – Great Idea or a Legal Minefield?

Although it gives the impression that it is the opposite of copyright, it is not. Copyleft is still a license in the legal sense. Ironically enough, a copyleft work still has copyright.

A copyleft license has five characteristics:

1. Free Use
2. Freeree Distribution
3. Free Modification and Derivation
4. Free Combination
5. Universal Application

When owners of IP want to share their work, they often shy away from putting it in the public domain which would entail that they forfeit their IP and all legal claims to their program or work. The legal problem with public domain is that once a program or work is part of it, anyone can take it, amend or adjust it, and copyright or patent it. 

Examples of copyleft license:

CC-SA

CC-SA is a small set of copyleft licenses rapidly growing in popularity, particularly in Free Culture communities rather than Open Source Software communities. It is a set of Creative Commons Share-Alike License. These copyleft terms for Creative Commons licenses are offered in two different Creative Commons licenses, providing the CC-BY-SA (Attribution/Share-Alike) and CC-BY-NC-SA (Attribution/Non-Commercial/Share-Alike).

GPL

By far the most prominent and popular copyleft license is the GNU General Public License, or GPL. In addition to the usual copyleft terms and preferential treatment (but not prescriptive requirement) for noncommercial uses, it adds additional restrictions and reinforcements of restrictions based on earlier versions.

MPL

The Mozilla Public License, or MPL, is used by Firefox Web browser and is hence one of the best-known pieces of open source software in the world.