Free and open-source software
Free and open-source software is software available under a license that gives users the right to use, share, modify, and distribute the software modified or not to everyone and provides the means to exercise those rights using the software's source code. FOSS is an inclusive umbrella term encompassing free software and open-source software. The rights guaranteed by FOSS originate from the "Four Essential Freedoms" of The Free Software Definition and the criteria of The Open Source Definition. All FOSS has publicly available source code, but not all source-available software is FOSS. FOSS is the opposite of proprietary software, which is licensed restrictively or has undisclosed source code.
The historical precursor to FOSS was the hobbyist and academic public domain software ecosystem of the 1960s to 1980s. Free and open-source operating systems such as Linux distributions and descendants of BSD are widely used, powering millions of servers, desktops, smartphones, and other devices. Free-software licenses and open-source licenses have been adopted by many software packages. Reasons for using FOSS include decreased software costs, increased security against malware, stability, privacy, opportunities for educational usage, and giving users more control over their own hardware.
The free software movement and the open-source software movement are online social movements behind widespread production, adoption and promotion of FOSS, with the former preferring to use the equivalent term free/libre and open-source software. FOSS is supported by a loosely associated movement of multiple organizations, foundations, communities and individuals who share basic philosophical perspectives and collaborate practically, but may diverge in detail questions.
Overview
Free and open-source software is an umbrella term for software that is considered free software and open-source software. The precise definition of the terms free software and open-source software applies them to any software distributed under terms that allow users to use, modify, and redistribute said software in any manner they see fit, without requiring that they pay the author of the software a royalty or fee for engaging in the listed activities.Although there is an almost complete overlap between free-software licenses and open-source-software licenses, there is a strong philosophical disagreement between the advocates of these two positions. The terminology of FOSS was created to be a neutral on these philosophical disagreements between the Free Software Foundation and Open Source Initiative and have a single unified term that could refer to both concepts, although Richard Stallman argues that it fails to be neutral unlike the similar term; "Free/Libre and Open Source Software".
Free software
's The Free Software Definition, adopted by the FSF, defines free software as a matter of liberty, not price, and that which upholds the Four Essential Freedoms. The earliest known publication of this definition of his free software definition was in the February 1986 edition of the FSF's now-discontinued GNU's Bulletin publication. The canonical source for the document is in the philosophy section of the GNU Project website., it is published in 40 languages.Four essential freedoms of free software
To meet the definition of free software, the FSF requires the software's licensing respect the civil liberties / human rights of what the FSF calls the software user's "Four Essential Freedoms".- The freedom to run the program as you wish, for any purpose.
- The freedom to study how the program works, and change it so it does your computing as you wish. Access to the source code is a precondition for this.
- The freedom to redistribute copies so you can help others.
- The freedom to distribute copies of your modified versions to others. By doing this, you can give the whole community a chance to benefit from your changes. Access to the source code is a precondition for this.
Open-source software
History
In the early decades of computing, particularly from the 1950s through the 1970s, software development was largely collaborative. Programs were commonly shared in source code form among academics, researchers, and corporate developers. Most companies at the time made their revenue from hardware sales, and software—including source code—was distributed freely alongside it, often as public-domain software.By the late 1960s and 1970s, a distinct software industry began to emerge. Companies started selling software as a separate product, leading to the use of restrictive licenses and technical measures—such as distributing only binary executables—to limit user access and control. This shift was driven by growing competition and the U.S. government's antitrust scrutiny of bundled software, exemplified by the 1969 antitrust case United States v. IBM.
A key turning point came in 1980 when U.S. copyright law was formally extended to cover computer software. This enabled companies like IBM to further enforce closed-source distribution models. In 1983, IBM introduced its "object code only" policy, ceasing the distribution of source code for its system software.
In response to the growing restrictions on software, Richard Stallman launched the GNU Project in 1983 at MIT. His goal was to develop a complete Free software operating system and restore user freedom. The Free Software Foundation was established in 1985 to support this mission. Stallman's GNU Manifesto and the Four Essential Freedoms outlined the movement's ethical stance, emphasizing user control over software.
The release of the Linux kernel by Linus Torvalds in 1991, and its relicense under the GNU General Public License in 1992, marked a major step toward a fully Free operating system. Other Free software projects like FreeBSD, NetBSD, and OpenBSD also gained traction following the resolution of the USL v. BSDi lawsuit in 1993.
In 1997, Eric Raymond's essay The Cathedral and the Bazaar explored the development model of Free software, influencing Netscape's decision in 1998 to release the source code for its browser suite. This code base became Mozilla Firefox and Thunderbird.
To broaden business adoption, a group of developers including Raymond, Bruce Perens, Tim O'Reilly, and Linus Torvalds rebranded the Free software movement as "Open Source." The Open Source Initiative was founded in 1998 to promote this new term and emphasize collaborative development benefits over ideology.
Despite initial resistance—such as Microsoft's 2001 claim that "Open-source is an intellectual property destroyer"—FOSS eventually gained widespread acceptance in the corporate world. Companies like Red Hat proved that commercial success and Free software principles could coexist.
Usage
Benefits over proprietary software
Personal control, customizability and freedom
Users of FOSS benefit from the Four Essential Freedoms to make unrestricted use of, and to study, copy, modify, and redistribute such software with or without modification. If they would like to change the functionality of software they can bring about changes to the code and, if they wish, distribute such modified versions of the software or often − depending on the software's decision making model and its other users − even push or request such changes to be made via updates to the original software.Privacy and security
Manufacturers of proprietary, closed-source software are sometimes pressured to building in backdoors or other covert, undesired features into their software. Instead of having to trust software vendors, users of FOSS can inspect and verify the source code themselves and can put trust on a community of volunteers and users. As proprietary code is typically hidden from public view, only the vendors themselves and hackers may be aware of any vulnerabilities in them while FOSS involves as many people as possible for exposing bugs quickly.Low costs or no costs
FOSS is often free of charge although donations are often encouraged. This also allows users to better test and compare software.Quality, collaboration and efficiency
FOSS allows for better collaboration among various parties and individuals with the goal of developing the most efficient software for its users or use-cases while proprietary software is typically meant to generate profits. Furthermore, in many cases more organizations and individuals contribute to such projects than to proprietary software. It has been shown that technical superiority is typically the primary reason why companies choose open source software.Drawbacks compared to proprietary software
Security and user-support
According to Linus's law, the more people who can see and test a set of code, the more likely any flaws will be caught and fixed quickly. However, this does not guarantee a high level of participation. Having a team of full-time professionals behind a commercial product can, in some cases, lead to more secure code than in a volunteer-driven FOSS project.Furthermore, publicized source code might make it easier for hackers to find vulnerabilities in it and write exploits. This however assumes that such malicious hackers are more effective than white hat hackers which responsibly disclose or help fix the vulnerabilities, that no code leaks or exfiltrations occur and that reverse engineering of proprietary code is a hindrance of significance for malicious hackers.