Copyleft

People make things like art and computer code.

Some people want to share these things. They use a rule called copyleft. This rule lets you copy and change work. You can even share it with friends.

But you must follow one big rule. If you change the work, you must share it too. This keeps the work free for everyone. It helps many people learn and grow together. Sharing makes the whole world better.

People make many things, like art and computer code.

Usually, creators use copyright laws to control their work. This lets them decide who can copy or change it. But some people want to share more freely. They use a special rule called copyleft.

Copyleft lets you use, change, and share a work. You can even do this for money. But there is one big rule. If you change the work, you must share it under the same rules. This means your new version stays free for others too.

Some people call this "reciprocal" because the sharing goes both ways.

Richard Stallman helped start this idea. In the 1980s, he wanted to stop "software hoarding." This is when companies keep code secret. He made the GNU General Public License to fix this. It was the first big copyleft license for software. Later, other groups made rules for art and books. One famous group is Creative Commons. They made the ShareAlike rule for things like pictures and writing. Now, copyleft helps many people work together.

Copyleft is a special way to use copyright law. Usually, copyright gives creators control over their work. It lets them decide who can copy or change it. Copyleft does something different. It grants freedoms to anyone who uses the work.

People can use the work for any purpose. They can also modify, copy, and share it. They can even charge a fee for it. However, there is one very important rule. Anyone who changes the work must use the same copyleft rules for their new version. This keeps the work free for everyone else too.

This rule is often called reciprocity. It means that the sharing goes both ways. If you improve a piece of software, you must share those improvements. You must also provide the source code to others. The source code is the set of instructions that tells a computer how to run a program.

By sharing this code, you help the whole community. This prevents people from taking free code and making it secret. Some people even call this a "viral" way of sharing. This is because the rules stay with the work as it grows and changes.

Many people helped develop these ideas over time. In 1976, Li-Chen Wang wrote a program called Palo Alto Tiny BASIC. It even used a phrase like "@COPYLEFT ALL WRONGS RESERVED." Later, Richard Stallman became a key leader in this movement. In 1984, he wanted to stop "software hoarding." This was when companies kept helpful code for themselves. In 1985, he wrote the GNU Manifesto. He also created the Emacs General Public License. This was the first major copyleft license for software. It later became the GNU General Public License, or GPL.

There are many different types of copyleft licenses today. The GNU General Public License is very popular for computer software. Other licenses work for things like art or books. For example, the Free Art License was born from meetings in France in 2000. Another famous group is Creative Commons. They started offering licenses in 2001. One of their rules is called "ShareAlike." This is used for things like pictures and documents. Even Wikipedia uses a Creative Commons license to stay copyleft.

Copyleft connects to how we share things in the digital world. It is different from the "public domain." In the public domain, no one owns the copyright at all. With copyleft, the author still owns the work. They just use their ownership to protect the rights of others. This creates a "gift economy" for many programmers. People contribute great work to gain experience or help their peers. It also helps prevent big companies from having a monopoly. This way, everyone can join in and build new things together.

Copyleft is a legal technique used to grant specific freedoms to anyone who uses a copyrighted work.

While standard copyright laws usually restrict how a work can be used, copyleft uses those same laws to ensure freedoms are preserved. These freedoms allow people to use a work for any purpose. They also include the ability to modify, copy, share, and redistribute the work. This can be done with or without a fee. Copyleft is used for many different things, including computer software, documents, art, and even scientific discoveries.

The mechanism of copyleft relies on a principle called reciprocity. When a person creates a work under a copyleft license, they impose a specific requirement on anyone who changes it. This requirement states that any derivative works must be released under a compatible copyleft license. This ensures that the original freedoms are passed down to every future user. Because these terms must stay with the work as it is modified, some people call these "viral" licenses. In the world of software, this often means the creator must also provide the source code. The source code is the set of instructions that allows others to study and change the program.

There are different ways to categorize these licenses. Copyleft licenses are often called protective or reciprocal licenses. This is different from permissive free software licenses, which allow people to take code and make it private. Copyleft prevents "open source hijacking," where someone takes free code and adds new restrictions to it. There are also different types of works that use copyleft. The GNU General Public License is designed for software. Other licenses, like the Free Art License or the Creative Commons ShareAlike condition, are meant for artistic or academic works like pictures and documents.

The history of copyleft includes several important moments and people. In May 1976, Li-Chen Wang published Palo Alto Tiny BASIC in Dr. Dobb's Journal. It included the phrase "@COPYLEFT ALL WRONGS RESERVED." However, the modern movement grew largely because of Richard Stallman. In 1984, Stallman wanted to stop "software hoarding," where companies kept useful code secret. He had a difficult experience when a company called Symbolics refused to share improvements they made to his Lisp interpreter. In 1985, Stallman wrote the GNU Manifesto and created the Emacs General Public License. This was the first major copyleft license and eventually evolved into the GNU General Public License, or GPL.

The term "Copyleft" itself has a unique origin. Stallman stated that the name came from Don Hopkins. In 1984 or 1985, Hopkins sent a letter that included the phrase "Copyleft – all rights reversed." This was a pun on the common legal phrase "all rights reserved." Over time, the movement expanded globally. In 2000, meetings in France called "Copyleft Attitude" led to the creation of the Free Art License. Shortly after, in 2001, the Creative Commons initiative began in the United States. They created licenses that include a "ShareAlike" (BY-SA) option, which functions as a copyleft condition for non-software works.

Copyleft provides specific economic and social incentives for creators. Instead of earning money through traditional royalties, many creators seek recognition from their peers. In the programming community, this is often described as a "gift economy." In this system, social power comes from how much an individual contributes to the community. Creating high-quality copyleft software can lead to valuable experience and future career opportunities. Additionally, the presence of quality copyleft software can force companies to improve their own products to compete. This can help prevent monopolies from dominating certain areas of technology.

Finally, copyleft relates to broader legal and social systems. It is distinct from the "public domain," where no one claims ownership of a work. In copyleft, the author still holds the copyright, but they use it to protect the rights of the public. These licenses must work within the existing legal frameworks of different countries. For example, laws regarding warranties vary between the United States and Europe. Because of this, some licenses like the European Union Public Licence (EUPL) are specifically designed to follow European rules. By using these legal tools, copyleft ensures that knowledge and tools remain available for everyone to use and improve.