Software Licenses
A software license is a legal instrument (usually by way of contract law, with or without printed material) governing the use or redistribution of software. Under United States copyright law, all software is copyright protected, in both source code and object code forms, unless that software was developed by the United States Government, in which case it cannot be copyrighted.[1] Authors of copyrighted software can donate their software to the public domain, in which case it is also not covered by copyright and, as a result, cannot be licensed.
A typical software license grants the licensee, typically an end-user, permission to use one or more copies of the software in ways where such a use would otherwise potentially constitute copyright infringement of the software owner’s exclusive rights under copyright.
Software licenses and copyright law
Most distributed software can be categorized according to its license type (see table).
Two common categories for software under copyright law, and therefore with licenses that grant the licensee specific rights, are proprietary software and free and open-source software (FOSS). The distinct conceptual difference between the two is the granting of rights to modify and re-use a software product obtained by a customer: FOSS software licenses both rights to the customer and therefore bundles the modifiable source code with the software (“open-source”), while proprietary software typically does not license these rights and therefore keeps the source code hidden (“closed source”).
In addition to granting rights and imposing restrictions on the use of copyrighted software, software licenses typically contain provisions that allocate liability and responsibility between the parties entering into the license agreement. In enterprise and commercial software transactions, these terms often include limitations of liability, warranties, and warranty disclaimers, and indemnity if the software infringes the intellectual property rights of anyone.
Unlicensed software outside the scope of copyright protection is either public domain software (PD) or software that is non-distributed, non-licensed, and handled as an internal business trade secret. Contrary to popular belief, distributed unlicensed software (not in the public domain) is fully copyright protected, and therefore legally unusable (as no usage rights at all are granted by a license) until it passes into the public domain after the copyright term has expired. Examples of this are unauthorized software leaks or software projects which are placed on public software repositories like GitHub without a specified license. As voluntarily handing software into the public domain (before reaching the copyright term) is problematic in some jurisdictions (for instance the law of Germany), there are also licenses granting PD-like rights, for instance, the CC0 or WTFPL.
Free and open-source software licenses
There are several organizations in the FOSS domain that give out guidelines and definitions regarding software licenses. Free Software Foundation maintains non-exhaustive lists of software licenses following The Free Software Definition and licenses which the FSF considers non-free for various reasons. The FSF distinguishes additionally between free software licenses that are compatible or incompatible with the FSF license of choice, the copyleft GNU General Public License. The Open Source Initiative defines a list of certified open-source licenses following The Open Source Definition. Also, the Debian project has a list of licenses that follow their Debian Free Software Guidelines.
Free and open-source licenses are commonly classified into two categories: Those with the aim to have minimal requirements about how the software can be redistributed (permissive licenses), and the protective share-alike (copyleft Licenses).
An example of a copyleft-free software license is the often used GNU General Public License (GPL), also the first copyleft license. This license is aimed at giving and protecting all users unlimited freedom to use, study, and privately modify the software, and if the user adheres to the terms and conditions of the GPL, freedom to redistribute the software or any modifications to it. For instance, any modifications made and redistributed by the end-user must include the source code for these, and the license of any derivative work must not put any additional restrictions beyond what the GPL allows.[24]
Examples of permissive free software licenses are the BSD license and the MIT license, which give unlimited permission to use, study, and privately modify the software, and include only minimal requirements on redistribution. This gives a user the permission to take the code and use it as part of closed-source software or software released under a proprietary software license.
It was under debate some time if public domain software and public domain-like licenses can be considered as a kind of FOSS license. 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 a very permissive FOSS 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.
references — Wikipedia