Dual-licensing

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Dual-licensing is the practice of distributing identical software under two different sets of terms and conditions. This may mean two different licenses, or two different sets of licenses. Software is sometimes offered under more than two licenses, in which cases tri-licensing or multi-licensing may be a more accurate term.

When software is dual-licensed, recipients can choose which terms they want to use or distribute the software under. The distributor may or may not apply a fee to either option.

The two usual motivations for dual-licensing are license compatibility and market segregation based business models.

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This is commonly done to support free software business models. In this model, one option is a proprietary software license, which allows the possibility of creating proprietary applications derived from it, while the other license is a copyleft free software/open-source license, thus requiring any derived work to be released under the same license. The copyright holder of the software then typically gives away the free/open source version of the software at no cost, and profits by selling licenses to commercial operations looking to incorporate the software into their own business.

Since in most cases only the copyright holder can change the licensing terms of a software, dual licensing is mostly used by companies that wholly own the software which they are licensing.

Dual licensing is used by the copyright holders of some free software packages advertising their willingness to distribute using both a copyleft free software license and a non-free software license. The latter license typically offers users the software as proprietary software or offers third parties the source code without copyleft provisions. Copyright holders are exercising the monopoly they're provided under copyright in this scenario, but also use dual licensing to discriminate the rights and freedoms different recipients receive.

Such licensing allows the holder to offer customisations, early releases, generate other derivative works or grant rights to third parties to redistribute proprietary versions all while offering everyone a free version of the software. Sharing the package as copyleft free software can benefit the copyright holder by receiving contributions from users and hackers of the free software community. These contributions can be the support of a dedicated user community, word of mouth marketing or modifications that are made available as stipulated by a copyleft license. However, a copyright holder's commitment to elude copyleft provisions and advertise proprietary redistributions risks losing confidence and support from free software users. [1] [2]

Examples include MySQL AB's database, Gaia Ajax Widgets, and Trolltech's Qt development toolkit.

A second use of dual-licensing with free software is for license compatibility, allowing code from differently licensed free software projects to be combined, or to provide users the preference to pick a license.

Examples include the source code of Mozilla Application Suite, Mozilla Thunderbird and Mozilla Firefox, which is tri-licensed under the Mozilla Public License (MPL), GNU General Public License (GPL) and GNU Lesser General Public License (LGPL);[1] and Perl, which is dual-licensed under the GPL and Artistic License.[2]

Dual licensing is also used by some distributors of non-free software. Sometimes this is done to proprietary software to segregate a market. By splitting people into multiple categories such as home users, professional users, and academic users, copyright holders can set different prices for each group. However, among proprietary software, it is more common "home edition" and "professional edition" be also differentiated by the software included, not just the license.

  1. ^ Mozilla Foundation. Mozilla Code Licensing. Retrieved on 2007-09-17.
  2. ^ The Perl Foundation. Perl Licensing - perl.org. Retrieved on 2007-09-17.

Retrieved from "http://en.wikipedia.org/wiki/Dual-licensing"
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