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Free and open-source software

Freely licensed software with open code

  • 14 min read
  • 6 chapters
A screenshot of free and open-source software (FOSS): Debian running the KDE Plasma desktop environment, Firefox, Dolphin file manager, VLC media player, LibreOffice Writer, GIMP, and KCalc.
Paowee · CC BY-SA 4.0

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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 (FOSS) 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(s) of the software a royalty or fee for engaging in the listed activities.

Free-software licenses and open-source-software licenses philosophical disagreement

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 (FSF) and Open Source Initiative (OSI) 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" (FLOSS).

Proponents of permissive and copyleft licenses disagree on whether software freedom should be viewed as a negative or positive liberty. Due to their restrictions on distribution, not everyone considers copyleft licenses to be free. Conversely, a permissive license may provide an incentive to create non-free software by reducing the cost of developing restricted software. Since this is incompatible with the spirit of software freedom, many people consider permissive licenses to be less free than copyleft licenses.

Free software

Richard Stallman'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. As of August 2017, 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 (freedom 0).
  • The freedom to study how the program works, and change it so it does your computing as you wish (freedom 1). Access to the source code is a precondition for this.
  • The freedom to redistribute copies so you can help others (freedom 2).
  • The freedom to distribute copies of your modified versions to others (freedom 3). 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

The Open Source Definition is used by the Open Source Initiative (OSI) to determine whether a software license qualifies for the organization's insignia for open-source software. The definition was based on the Debian Free Software Guidelines, written and adapted primarily by Bruce Perens. Perens did not base his writing on the Four Essential Freedoms of free software from the Free Software Foundation, which were only later available on the web. Perens subsequently stated that he felt Eric Raymond's promotion of open-source unfairly overshadowed the Free Software Foundation's efforts and reaffirmed his support for free software. In the following 2000s, he spoke about open source again.

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