Table of contents
- The concept of copyleft: the roots of free software
- From copyright to copyleft: a paradigm shift
- The four essential freedoms of free software
- Examples of copyleft licenses: GPL and Creative Commons
- From philosophy to practice: the birth of Open Source
- Open Source Initiative: a structured definition
- Freedom, cooperation, innovation
The concept of copyleft: the roots of free software
Before delving into the Open Source model, it is essential to start with the concept of copyleft, theorized by Richard Stallman, a key figure in computer science known for his commitment to digital freedom and his central role in the birth of the free software movement.
The New York-based programmer and activist launched the GNU project in 1983 (GNU stands for “GNU’s Not Unix”), with the goal of developing an operating system entirely composed of non-proprietary, freely available software.
Two years later, he founded the Free Software Foundation (FSF), a non-profit organization dedicated to promoting and protecting software freedom. In 1989, Stallman successfully released the first version of the GNU General Public License (GPL), a license that had a lasting and far-reaching impact on the diffusion of free software.
From copyright to copyleft: a paradigm shift
The term “copyleft” was coined as a play on the word “copyright”, a legal concept in common law systems that protects authorship, typically associated with the phrase “all rights reserved” and the circled “c” symbol.
Copyleft, by contrast, uses the phrase “all rights reversed” and a reversed “c”, signaling a new way to manage intellectual property rights not only for software but also for other creative works. Its core mission is to safeguard four fundamental freedoms: the freedom to run, study, modify, and share the software.
Works protected by copyright can only be used with the formal authorization of the rights holder, usually granted in exchange for a fee. In the traditional model of proprietary software, copyright is used to prohibit modifications, decompilation, creation of derivative works, redistribution, and code analysis. In this model, the work is protected by restricting the user’s (licensee’s) freedom.
In Stallman’s manifesto “What is Copyleft?” (available at https://www.gnu.org/licenses/copyleft.html), he states: “Proprietary software developers use copyright to take away the users’ freedom; we use copyright to guarantee their freedom.”
Indeed, the free software movement reverses this logic by using copyright proactively: free licenses (such as the GNU GPL) affirm that anyone may use, copy, or modify the work, provided that the same freedoms are preserved for future users.
- This is the core idea of copyleft
The prohibition of privatizing a work that was born free, and the obligation to keep it accessible to future users. In practice, anyone who modifies or expands a copyleft-licensed work must distribute the resulting product under the same license. This ensures the continuous development of open works, freely available and modifiable by anyone wishing to contribute.
By applying a copyleft license, the author grants anyone the right to access and freely modify the source code (and the work as a whole), provided that any derived version is distributed under the same terms. This prevents third parties from unfairly claiming ownership of the original work or its modifications.
The four essential freedoms of free software
Stallman’s words are crucial for understanding the concept of Free Software and the philosophical principles it embodies: “The term ‘free software’ is sometimes misunderstood: it has nothing to do with price. It is about freedom. Here, then, is the definition of free software. A program is free software for you, a particular user, if”:
- You have the freedom to run the program as you wish, for any purpose.
- You have the freedom to modify the program to suit your needs. (To make this freedom practical, you must have access to the source code.)
- You have the freedom to redistribute copies, either free of charge or for a fee.
- You have the freedom to distribute modified versions so that the community can benefit from your improvements.” (Source: The GNU Project – https://www.gnu.org/gnu/thegnuproject.html.en)
Examples of copyleft licenses: GPL and Creative Commons
Some of the most well-known and widely used copyleft licenses include:
- GNU General Public License (GPL), created by Stallman to ensure that software remains free over time, even when modified or redistributed by third parties.
- Creative Commons Attribution-ShareAlike (CC BY-SA), often used for creative works other than software, allows both commercial and non-commercial use, provided that derivative works are shared under the same license, maintaining an equal level of openness.
From philosophy to practice: the birth of Open Source
During the 1990s, Stallman’s vision of free software found success in academic and activist circles, but faced resistance in the U.S. business world. The term “free” was often misinterpreted as “free of charge” rather than “freedom-based.”
To make open licensing more attractive to businesses, in 1997, figures like Bruce Perens and Eric S. Raymond introduced a new narrative, focusing on the practical and economic advantages of openness. Thus, the term Open Source was born, literally meaning “Open Source code”, intended to overcome ideological resistance and appeal to commercial sectors.
The shift gained momentum when Netscape released the source code of its browser, prompting a debate on the need for more flexible licenses than the GNU GPL. Support from tech giants like IBM, HP, Sun Microsystems, and Netscape helped establish Open Source as a credible and effective industrial approach to software production.
Open Source Initiative: a structured definition
The Open Source Initiative (OSI) built upon the four freedoms of free software — the freedom to run, modify, redistribute, and improve software — and provided a formal definition of what constitutes Open Source software.
A key principle was added: the absence of discrimination against persons or groups and against fields of endeavor. When a license satisfies these requirements, the software can be called Free and Open Source Software (FOSS) — a model that combines the ethical dimension of free software with the collaborative and operational strengths of Open Source. Today, the OSI recognizes over 70 such licenses.
OSI criteria for an Open Source license
According to the OSI’s Open Source Definition (https://opensource.org/osd), an Open Source license must:
- Not restrict any party from selling or giving away the software, even when bundled with software from different developers. While distribution may involve charging for physical media or support services, the software’s freedoms — use, modification, redistribution, access to source code — must remain intact for all users. No royalties or fees may be required to exercise these rights.
- Guarantee access to the source code and prevent code obfuscation.
- Require that derivative works be distributed under the same license.
- Allow for the distribution of software based on modified code, even if the license restricts direct redistribution of altered code (e.g., by requiring that changes be distributed as separate patch files).
Licensing is essential not only for encouraging cooperation, but also for preventing abuse of Open Source software — such as opportunistic behavior or unfair exploitation of others’ work without genuine contributions to the collective project.
Freedom, cooperation, innovation
With an Open Source license, the copyright holder grants the user fundamental rights to access, modify, use, and redistribute the software. What began as a radical vision to counter the dominance of major corporations has now become a cornerstone of innovation in key areas of IT — from the Linux operating system to modern development tools.
Understanding what an Open Source license is, how it works, and why it matters is crucial not just for developers, but also for businesses, public institutions, and digital citizens. Open Source licenses are not just legal instruments: they are the glue that binds together the largest collaborative development community in history.
