An open-source license is a type of license for computer software and other products that allows the source code, blueprint or design to be used, modified and/or shared under defined terms and conditions. This allows end users and commercial companies to review and modify the source code, blueprint or design for their own customization, curiosity or troubleshooting needs. Open-source licensed software is mostly available free of charge, though this does not necessarily have to be the case. Licenses which only permit non-commercial redistribution or modification of the source code for personal use only are generally not considered as open-source licenses. However, open-source licenses may have some restrictions, particularly regarding the expression of respect to the origin of software, such as a requirement to preserve the name of the authors and a copyright statement within the code, or a requirement to redistribute the licensed software only under the same license (as in a copyleft license). There has previously been debates about whether open source licenses, which permit copyholders to use, transfer, and modify software, have adequate consideration, should be viewed by the courts as legally enforceable contracts. While some academics have argued that open source licenses are not contracts because there is no consideration, others have argued that the significant societal value provided by the role that open source licenses play in promoting software development and improvement by facilitating access to source code offers adequate consideration. One popular set of open-source software licenses are those approved by the Open Source Initiative (OSI) based on their Open Source Definition (OSD).


The Free Software Foundation has related but distinct criteria for evaluating whether or not a license qualifies software as free software. Most free software licenses are also considered open-source software licenses. In the same way, the Debian project has its own criteria, the Debian Free Software Guidelines, on which the Open Source Definition is based. In the interpretation of the FSF, open-source license criteria focus on the availability of the ''source code'' and the ability to modify and share it, while free software licenses focuses on the user's freedom to use the ''program'', to modify it, and to share it. Source-available licenses ensure source code availability, but do not necessarily meet the user freedom criteria to be classified as free software or open-source software.

Public domain

Around 2004, lawyer Lawrence Rosen argued in the essay ''"Why the public domain isn't a license"'' software could not truly be waived into the public domain and can't therefore be interpreted as very permissive open-source license, a position which faced opposition by Daniel J. Bernstein and others. In 2012, the dispute was finally resolved when Rosen accepted the CC0 as an open-source license, while admitting that contrary to his previous claims, copyright can be waived away, backed by Ninth Circuit decisions.

See also

* Beerware * Comparison of free and open-source software licenses * Free-software license * Jacobsen v. Katzer – a ruling which states that legal copyrights can have $0 value and thereby supports all licenses, both commercial and open-source * List of free-content licenses * Multi-licensing * Open-source model * Open-source software * Proprietary software * Software license * * *


External links

The Open Source Initiative
*An online version of Lawrence Rosen's book ''Open Source Licensing: Software Freedom and Intellectual Property Law'' ().
Understanding Open Source Software – by Red Hat's Mark Webbink, Esq.
— an overview of copyright and open source. {{FOSS * Category:Terms of service Category:Free culture movement