- Dual-licensing
Dual-licensing is the practice of distributing
software under two different sets of terms and conditions. This may mean two differentlicenses , 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.Business models
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 acopyleft 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. This model can be compared toShareware . [http://linuxinsider.com/story/38172.html] [http://linux.sys-con.com/read/49061.htm]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 acopyleft free software license and a non-free software license. The latter license typically offers users the software asproprietary software or offers third parties the source code without copyleft provisions. Copyright holders are exercising the monopoly they're provided undercopyright 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. [http://www.gnu.org/philosophy/netscape-npl.html] [http://www.gnu.org/philosophy/apsl.html]Examples include
MySQL AB 's database, Mozilla Firefox, andTrolltech 's Qt development toolkit.License compatibility
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 andMozilla Firefox , which is tri-licensed under theMozilla Public License (MPL),GNU General Public License (GPL) andGNU Lesser General Public License (LGPL); [cite web | url=http://www.mozilla.org/MPL/ | title=Mozilla Code Licensing | accessdate=2007-09-17 | author=Mozilla Foundation ] andPerl , which is dual-licensed under the GPL andArtistic License . [cite web | url=http://dev.perl.org/licenses/ | title=Perl Licensing - perl.org | accessdate=2007-09-17 | author=The Perl Foundation ]Market segregation in proprietary software
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.
References
External links
* [http://www.oss-watch.ac.uk/resources/duallicence2.xml Dual Licensing information] from
OSS Watch
* Article " [http://linuxjournal.com/node/1000069 Does dual licensing threaten free software?] " by Glyn Moody
* Article " [http://linuxjournal.com/article/5923 The Dual-Licensing Model] " by Don Marti
* Article " [http://linuxinsider.com/story/38172.html Dual Licensing: Having Your Cake and Eating It Too] " by Philip H. Albert
* Article " [http://linux.sys-con.com/read/49061.htm Dual-Licensing Open Source Business Models] " by Heather Meeker
* Article " [http://www.itmanagersjournal.com/feature/377 How to use open source as a power marketing tool] " by John Koenig
* Paper " [http://opensource.mit.edu/papers/valimaki.pdf Dual Licensing in Open Source Software Industry] " by Mikko Välimäki
* [http://producingoss.com/html-chunk/dual-licensing.html Dual Licensing Schemes]
* " [http://www.softwarefreedom.org/resources/2007/gpl-non-gpl-collaboration.html#x1-90004 Should code be “dual licensed” under the GPL and a permissive license?] " by Software Freedom Law Center
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