Open-source software is licensed so that anyone can use, alter, and share it. An open-source license (OSS) is a legal contract that determines the copyright of software. Open-source licenses have many practical uses for business and development. The open-source movement has solved many problems that plagued software developers in the past, particularly through crowdsourcing.
Rapid development is much easier when millions of users can help developers test and improve the software. One of the most well-known open-source projects is Linux, a free operating system kernel built on top of the GNU operating system. Linux uses the GPL version 2 license. All open-source licenses are intended to govern how the software will be used. This includes:
- Private Use: the freedom to use and change software for non-commercial purposes.
- Distribution: sharing for commercial or non-commercial use.
- Linking: linking to free and proprietary sources.
- Patent Grants: rights to intellectual property granted by the government.
- Sublicensing: an agreement in which the owner of something allows people to use their software to create new things so long as whatever they create is also distrubuted under GPL.
- Trademarks: a symbol or word that represents an organization or product.
Open-Source Software vs Free Software
Just because software has an open-source license, does not mean it is free. It may be easy to interpret the term “open-source” to mean “free”. Both of these terms have complex definitions that are constantly changing. While all free software licenses are technically open-source, not all open-source licenses are free.
Legal interpretations and enforcement of the terms and conditions contained in any given open-source license will depend on the legal jurisdiction protecting the copyright. It also depends on the country connected to that jurisdiction. The seeds of open-source licensing can be traced to free, copyleft licenses created in the United States during the 1980s.
The creation of the Open Source Initiative (OSI) in 1998 has helped shape the landscape of the open-source software licensing today. Below are some sources with helpful definitions of key terms, organizational bodies, and historical landmarks related to open-source licensing.
- A Primer on Open-Source Software Licenses
- Open Source Initiative (OSI)
- Free Software Foundation
- History of Unix
- History of the GNU Operating System
- Source Code
- Free and Open-Source Software (FOSS)
- Open-Source Software
- Proprietary Software
- Permissive Software License.
Popular Open-Source Licenses
Here are the most popular open-source licenses currently available:
- Academic Free License: the Academic Free License gives you copyright as long as you include the original source code, a statement saying you modified it, and any trademarks or copyrights associated with the original.
- Adaptive Public License: an adaptable copyleft license template that users can modify to suit their needs.
- Apache Software License: used by the Apache Software Foundation from 1995 to 1999. This license is only applicable with earlier versions of Apache Software.
- Apache License 2.0: a revision on a previous version of the Apache license. It was approved in 2004. For more information, see Understanding the 2.0 License.
- Apple Public Source License: considered a weaker version of the GPL. This is a free and open-source license.
- Artistic license: written by the Perl Foundation, this license is intended to give the copyright holder control over the development of a software “Package” while still keeping it open-source and free.
- Attribution Assurance Licenses: an adaptation of the original BSD licenses, these licenses are intended to use with free open-source software.
- BSD Licenses: stands for Berkley Software Distribution. Use of the term “BSD license” refers to licenses that use versions of a BSD license as a template.
- New BSD license: also goes by the name Modified BSD license. These licenses are compatible with free open-source software licenses and proprietary software licenses.
- CCO: this is basically a no copyright license. Software under a CCO is under public domain.
- Computer Associates Trusted Open-Source License 1.1: this permissive license containing plenty of restrictions was written by CA Technologies, one of the largest independent software corporations in the world.
- Common Development and Distribution License: a free and open-source license based on the Mozilla Public License. This is one of the most popular free software licenses in use.
- Common Public License 1.0: this was IBM’s updated version of their first open-source license, the IBM Public License (IPL). It was written to enhance collaboration by generalizing the terms of the IPL.
- Eclipse Public License: written for the Eclipse Foundation for the use of commercial friendly open-source software collaboration.
- Educational Community License: based on the Apache 2.0 license. This license was created to suit the needs of the online academic community.
- Eiffel Forum License V2: this is a short license that has since been depreciated by other more popular licenses.
- Entessa Public License: created for the openSEAL project, a .NET framework development platform.
- EU DataGrid Software License: a free open-source software license created by the European Commision. It’s used for software distribution.
- Fair License: this is the shortest license ever approved by the Open Source Initiative. It is purposefully vague and obtuse. It’s intended for fair use for any kind of media.
- Frameworx License: a GPL compatible license used to control the distribution of open-source software.
- GNU Affero General Public License: copyleft software designed specifically to work with network server software and the community.
- GNU General Public Licenses: also known as GPL or GNU GPL, the GNU General Public license is one of the oldest and most widely used copyleft license. The link takes you to older versions of the GPL. These licenses are influential precursors to many other free open-source licenses. The GPL was originally created for the GNU operating system — a Unix-like operating system, founded by Richard Stallman in the early 1980s. The goal of the GPL license is to keep software free. GPL licenses allow for commercial as well as non-commercial use.
- GNU Library or “Lesser” General Public License (LGPL): this includes all versions of the GPL after version 2. Yes it’s very confusing, see GNU.org’s section on license compatibility for more information.
- IBM Public License: abbreviated as IPL, this is IBMs first open-source license. The IBM public license is a modified version of the GPL.
- Lucent Public License: originally written for Plan 9, an heir to Unix created by Bell-Labs. Plan 9 has also been released under the GPL v2 license to attract developers.
- Microsoft Public License: this open-source license was approved by the Open Source Initiative in 2007.
- MIT license: A simple permissive software license used by the Massachusetts Institute of Technology many times over. It allows you to do just about anything you want with the software. There are many descendants of this license. The jQuery project uses a version of the MIT license.
- Motosoto License: this open-source license applies to web portals. It was originally for community portal software and is protected under Dutch copyright law.
- Mozilla Public License: this license was created to suit the needs of Mozilla, a free software project created by Netscape users.
- NASA Open-Source Agreement 1.3: this license is used by NASA for some of their software. To use software under this license you need to register with the government and specify how you are going to use the software.
- Naumen Public License: published by Naumen, a software as service provider. The license limits use in order to protect the author of the software.
- NetHack General Public License: the NGPL is a copyleft derivative of GPL written for NetHack, a computer game released in 1987.
- Nokia Open-Source License: based on the Mozilla Public License, this open-source license requires that disputes be settled by the Judicial System of Finland.
- OCLC Research Public License 2.0: created by OCLC Research in order to develop new solutions for libraries and archives. OCLC now uses the Apache 2.0 license.
- OpenContent License: this was created by the OpenContent (OC) movement. It allows works to be distributed without charge as long as they are done so for free and that the copyright notice is published with it “conspicuously and appropriately.” Modified works are also covered under the same conditions with the extra stipulation that it carry “prominent notices” that the work was changed and the exact nature of the change.
- Open Group Test Suite License: gives the copyright holder control over the artistic development of a software package while testing for bugs.
- Open Software License: another type of copyleft license that requires that you disclose the original source code with any copies shared.
- PHP License: PHP, the popular web-programming language, is distributed under this license.
- Python License (CNRI Python License): Python is a popular programming language. This is a portion of the full Python license that addresses its affiliation with the Cororation for National Research Initiatives (CNRI).
- Python Software Foundation License: a permissive license used for the distribution of the Python project software. Suitable to modify for a variety of different types of software.
- Qt Public License (QPL): Qt is a framework for developing applications across multiple platforms. This license is a modified BSD 2-Clause License.
- RealNetworks Public Source License: this open-source license has strict rules. RealNetworks also reserves the rights to use any changes you make to the software under this license.
- Reciprocal Public License: another offshoot of the GPL license, the Reciprocal Public License is a copyleft license that is intended to keep software free and open-source.
- Ricoh Source Code Public License: a permissive software license written for Ricoh Innovations Corp. This license grants considerable protection for the author.
- Ruby License: this along with the 2 Clause BSD license outline the terms which you can redistribute or modify the Ruby programming language.
- The Sleepycat License: a free and GPL compatible license that can be found in Berkley DB software. Also known as the Berkley Database License.
- Sun Industry Standards Source License (SISSL): a free and open-source license used by Sun Microsystems that has been retired since 2005.
- Sun Public License: influenced by the Mozilla Public License, the Sun Public License is approved as a free software licenses by the FSF.
- University of Illinois/NCSA Open-Source License: a short license that gives users plenty of freedom when they distribute software.
- Vovida Software License: this is another brief license that enables people to freely distribute software.
- W3C License: a license created for the World Wide Web Consortium It is an intellectual property disclaimer to protect the author.
You Got All That?
That’s a lot of open-source license to process. Even so, knowing what’s available can help to better guide your decisions going forward.
Further Reading and Resources
We have more guides, tutorials, and infogragphics related to all things computer and internet:
- The History of Search Engines: a thorough history of how we got from manually curated link lists to Google and beyond.
- How to Spot a Fake Website: before handing over your money to a website, find out if you can trust it.
- How Game Makers Earn Millions — 99¢ at a Time: learn about the multi-billion dollar game industry that you are funding pennies at a time.
Ultimate Guide to Copyright
If you really want to understand copyright, we’ve created a great resource, The Ultimate Guide to Copyright And it really is the ultimate guide; it will tell most of what you need to know. After that, you’ll probably need a lawyer.