you thought copyright was the only thing you needed to know.
you were so wrong.

What the Hell is Copyleft?
Copyleft is a play on the word copyright to describe the practice of using copyright law to remove restrictions on distributing copies and modified versions of a work for others and requiring that the same freedoms be preserved in modified versions.

Copyleft is a form of licensing and can be used to modify copyrights for works such as computer software, documents, music and art. In general, copyright law allows an author to prohibit others from reproducing, adapting, or distributing copies of the author's work. In contrast, an author may, through a copyleft licensing scheme, give every person who receives a copy of a work permission to reproduce, adapt or distribute the work as long as any resulting copies or adaptations are also bound by the same copyleft licensing scheme. A widely used and originating copyleft license is the GNU General Public License. Similar licenses are available through Creative Commons—called Share-alike.

Copyleft can also be characterized as a copyright licensing scheme in which an author surrenders some but not all rights under copyright law. Instead of allowing a work to fall completely into the public domain (where no copyright restrictions are imposed), copyleft allows an author to impose some, but not all, copyright restrictions on those who want to engage in activities that would otherwise be considered copyright infringement. Under copyleft, copyright infringement can be avoided if the would-be infringer perpetuates the same copyleft scheme. For this reason copyleft licenses are also known as "reciprocal" licenses.

While copyright law protects the rights of the creator by providing control of distribution and modification, the idea of copyleft is to grant subjective libre freedom to end users. Copyleft licenses specify clauses which explicity remove those restrictions the creator considers to not provide libre freedom to the end user. In software, open source copyleft licenses place the primary restriction that information helpful in supporting modification of software (e.g. source code) must be made available to a user with a copy of the licensed software and allows the original author to be acknowledged. [link]

in short : "Copyleft is a general method for making a program or other work free, and requiring all modified and extended versions of the program to be free as well." [link]

How Do I Apply copyleft?
Common practice for using copyleft is to codify the copying terms for a work with a license. Any such license typically gives each person possessing a copy of the work the same freedoms as the author, including (from the Free Software Definition):

1. the freedom to use and study the work,
2. the freedom to copy and share the work with others,
3. the freedom to modify the work,
4. and the freedom to distribute modified and therefore derivative works.

These freedoms do not ensure that a derivative work will be distributed under the same liberal terms. In order for the work to be truly copyleft, the license has to ensure that the author of a derived work can only distribute such works under the same or equivalent license.

In addition to restrictions on copying, copyleft licenses address other possible impediments. These include ensuring the rights cannot be later revoked and requiring the work and its derivatives are provided in a form that facilitates modification. In software, this requires that the source code of the derived work is made available together with the software itself.

Copyleft licenses necessarily make creative use of relevant rules and laws. For example, when using copyright law, those who contribute to a work under copyleft usually must gain, defer or assign copyright holder status. By submitting the copyright of their contributions under a copyleft license, they deliberately give up some of the rights that normally follow from copyright, including the right to be the unique distributor of copies of the work.

Some laws used for copyleft licenses vary from one country to another, and may also be granted in terms that vary from country to country. For example, in some countries it is acceptable to sell a software product without warranty, in standard GNU GPL style (see articles 11 and 12 of the GNU GPL version 2), while in most European countries it is not permitted for a software distributor to waive all warranties regarding a sold product. For this reason the extent of such warranties are specified in most European copyleft licenses. Regarding that, see the CeCILL license, a license that allows one to use GNU GPL (see article 5.3.4 of CeCILL) in combination with a limited warranty (see article 9 of CeCILL).

Types of copyleft and relation to other licenses
Copyleft is a distinguishing feature of some free software licenses. Many free software licenses are not copyleft licenses because they do not require the licensee to distribute derivative works under the same license. There is an ongoing debate as to which class of license provides the greater degree of freedom. This debate hinges on complex issues such as the definition of freedom and whose freedoms are more important, or whether to maximize the freedom of all potential future recipients of a work (freedom from the creation of proprietary software). Non-copyleft free software licenses maximize the freedom of the initial recipient (freedom to create proprietary software).

In common with the Creative Commons share-alike licensing system, GNU's Free Documentation License allows authors to apply limitations to certain sections of their work, exempting some parts of their creation from the full copyleft mechanism. In the case of the GFDL, these limitations include the use of invariant sections, which may not be altered by future editors. The initial intention of the GFDL was as a device for supporting the documentation of copylefted software. However, the result is that it can be used for any kind of document.

Strong and weak copyleft
The copyleft governing a work is considered to be "stronger", to the extent that the copyleft provisions can be efficiently imposed on all kinds of derived works. "Weak copyleft" refers to licenses where not all derived works inherit the copyleft license; whether a derived work inherits or not often depends on the manner in which it was derived.

"Weak copyleft" licenses are generally used for the creation of software libraries, to allow other software to link to the library, and then be redistributed without the legal requirement for the work to be distributed under the library's copyleft license. Only changes to the weak copylefted software itself become subject to the copyleft provisions of such a license, not changes to the software that links to it. This allows programs of any license to be compiled and linked against copylefted libraries such as glibc (the GNU project's implementation of the C standard library), and then redistributed without any re-licensing required.

The most well known free software license that uses strong copyleft is the GNU General Public License. Free software licenses that use "weak" copyleft include the GNU Lesser General Public License and the Mozilla Public License. Examples of non-copyleft free software licenses include the X11 license, Apache license and the BSD licenses.

The Design Science License is a strong copyleft license that can apply to any work that is not software or documentation, such as art, music, sports photography, and video. It is hosted on the Free Software Foundation website's license list, but it is not considered compatible with the GPL by the Free Software Foundation.

Full and partial copyleft
"Full" and "partial" copyleft relate to another issue: Full copyleft exists when all parts of a work (except the license itself) may only be modified and distributed under the terms of the work's copyleft license. Partial copyleft exempts some parts of the work from the copyleft provisions, thus permitting distribution of some modifications under terms other than the copyleft license, or in some other way does not impose all the principles of copylefting on the work. For example, the GPL linking exception made for some software packages.

Share-alike
Share-alike imposes the requirement that any freedom that is granted regarding the original work must be granted on exactly the same or compatible terms in any derived work: this implies that any copyleft license is automatically a share-alike license, but not the other way around, as some share-alike licenses include further restrictions, namely prohibiting commercial use. Some permutations of the Creative Commons licenses are examples of share-alike.

Is Copyleft Similar to Viral Licensing?
Copyleft licenses are sometimes referred to as viral copyright licenses, because any works derived from a copyleft work must themselves be copyleft when distributed. The term "General Public Virus", or "GNU Public Virus" (GPV), has a long history on the Internet, dating back to shortly after the GPL was first conceived. Many BSD License advocates used the term derisively in regards to the GPL's tendency to absorb BSD licensed code without allowing the original BSD work to benefit from it, while at the same time promoting itself as "freer" than other licenses. More recently, Microsoft has used language with this term. The term "viral" is used as an analogy of computer viruses. According to FSF compliance engineer David Turner, it creates a misunderstanding and a fear of using copylefted free software.

Popular copyleft licenses, such as the GPL, have a clause allowing components to interact with non-copyleft components as long as the communication is abstract, such as executing a command-line tool with a set of switches or interacting with a Web server. As a consequence, even if one module of an otherwise non-copyleft product is placed under the GPL, it may still be legal for other components to communicate with it normally. This allowed communication may or may not include reusing libraries or routines via dynamic linking — some commentators say it does, the FSF asserts it does not and explicitly adds an exception allowing it in the license for the GNU Classpath re-implementation of the Java library.

Commercial Use of Copyleft Works
Commercial advantage of copyleft works differs from traditional commercial advantage of Intellectual Property Rights (IPR). One way to make money with copylefted works is to sell consultancy and support for users of a copylefted work. Generally, financial profit is expected to be much lower in a "copyleft" business than in a business using proprietary works. Another way is to use the copylefted work as a commodity tool or component to provide a service or product. Forthcoming Motorola mobile phones, for example, will be Linux based products. Firms with proprietary products can make money by exclusive sales, by single and transferable ownership, and litigation rights over the work. [link]

Development
The competitiveness of copylefted works to proprietary ones is heightened for businesses able to adopt any of a variety of copylefted products that are already written and therefore lowering software development costs. Commercial ventures are able to use their resources to make revenues with the software in other ways, and without the worry of other companies getting an unfair advantage.

Copyleft enables volunteer programmers and organizations to feel involved and contribute to software and feel confident any future derivatives will remain accessible to them, and that their contributions are part of a larger goal, like developing the kernel of an OS. Copylefting software makes clear the intent of never abusing or hiding any knowledge that is contributed. Copyleft also ensures that all contributing programmers and companies cannot fork proprietary versions to create an advantage over another.

The argument for investments in research and development for copyleft businesses may seem weak, by not having exclusivity over the profits gained from the result. Economically, copyleft is considered the only mechanism able to compete with monopolistic firms that rely on financial exploitation of copyright, trademark and patent laws.

Distribution
Commercial distributors of Linux-based systems (like Red Hat and Mandriva) might have had some ups and downs in finding a successful construction (or business model) for setting up such businesses, but in time it was shown to be possible to base a business on a commercial service surrounding a copylefted creation. One well-known example is Mandrake, which was one of the first companies to succeed on the stock market after the implosion of large parts of the IT market in the early 21st century. They also had success in convincing government bodies to switch to their flavor of Linux.

However, apart from rare exceptions like Debian, most Linux distributors don't limit their business to copylefted software. There appears to be no real reason why an exploitation of commercial services surrounding copylefted creations would not be possible in small-scale business, which as a business concept is no more complex than making money with a "public domain" recipe for brewing coffee—successfully exploited by so many cafeteria owners. However, there are few examples so far of SMEs having risked such a leap for their core business. UserLinux, a project set up by Bruce Perens, supports the emergence of such small-scale business based on free software, that is, copylefted or otherwise freely licensed computer programs. The UserLinux website showcases some case studies and success stories of such businesses.

Art
In art, making commercial services out of a copylefted creation is more difficult to do in practice than in software development. Public performances could be considered as one of a few possibilities of providing such "services".

The music industry objected to peer-to-peer file exchanging software, but the Electronic Frontier Foundation gave some suggestions to resolve the issue.[2]

Objections to the appropriation of ideas for commerce believe intellectual works should not be compared to material property. Giving someone a physical object results in lost possession and control of that thing and can require asking for something in return, payment or barter. But when someone gives an idea to someone, they lose nothing, and need not ask for anything in return.

Often copylefted artistic creations can be seen to have a (supporting) publicity function, promoting other, more traditionally copyrighted creations by the same artist(s). Artists sticking to an uncompromising copylefting of the whole of their artistic output, could, in addition to services and consultancy, revert to some sort of patronage (sometimes considered as limiting artistic freedom), or to other sources of income, not related to their artistic production (and so mostly limiting the time they can devote to artistic creation too). The least that can be said is that copylefting in art tends toward keeping the art thus produced as much as possible out of the commercial arena—which is considered as an intrinsic positive goal by some.

Some artists use copyleft licenses such as the Creative Commons Attribution-NonCommercial-ShareAlike license that don't allow commercial use. In this way they can choose to sell their creations without having to compete with others selling copies of the same works.

Where copylefted art has a large audience of modest means or a small audience of considerable wealth, the act of releasing the art may be offered for sale.

Read These too
Copyleft: Pragmatic Idealism
Article: Working Without Copyleft by Bjørn Reese and Daniel Stenberg

Previous Articles on Copyright
PROTECT YOUR WORKS, COPYRIGHT YOURSELF.

UPCOMING NEWS ARTICLES
* All rights reversed
* Anti-copyright
* Creative Commons licenses
* Free content
* Free Culture movement
* Free Software Foundation
* GNU General Public License
* Open content
* Permissive free software licence
* Public domain
* Share-alike

hope you learned something new

xoxo,
shryne