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MIT License/X11 license
Author	Massachusetts Institute of Technology
Version	N/A
Copyright	Public Domain
Published	1988
DFSG compatible	Yes
Free software	Yes
OSI approved	Yes
GPL compatible	Yes
Copyleft	No
Linking from code with a different license	Yes

The MIT License is a free software license originating at the Massachusetts Institute of Technology (MIT). It is a permissive license, meaning that it permits reuse within proprietary software on the condition that the license is distributed with that software, and GPL-compatible, meaning that the GPL permits combination and redistribution with software that uses the MIT License.

According to the Free Software Foundation, the MIT License is more accurately called the X11 license, since MIT has used many licenses for software and the license was first drafted for the X Window System.^[1]

Software packages that use the MIT License include Expat, PuTTY, Mono development platform class libraries, Ruby on Rails, Lua 5.0 onwards and the X Window System, for which the license was written.

Some software packages dual license their products under the MIT License, such as older versions of the cURL library, which allowed recipients to choose either the Mozilla Public License or the MIT License.

Contents 1 License terms 2 Modified versions of the license 3 Comparison to other licenses 4 See also 5 External links 6 References

The license is as follows:

Copyright (c)  

Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documentation
files (the "Software"), to deal in the Software without
restriction, including without limitation the rights to use,
copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following
conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.

The license can be modified to suit particular needs. For example, the Free Software Foundation agreed in 1998 to use a modified MIT License for ncurses, which adds this clause:^[2]

Except as contained in this notice, the name(s) of the above copyright holders shall not be used in advertising or otherwise to promote the sale, use or other dealings in this Software without prior written authorization.

The XFree86 Project uses a modified MIT License for XFree86 version 4.4 onward. The license includes a BSD-style advertising clause that requires attribution in software documentation.^[3] The Free Software Foundation contends that this addition is incompatible with the GPL.^[4][5]

The end-user documentation included with the redistribution, if any, must include the following acknowledgment: "This product includes software developed by The XFree86 Project, Inc (http://www.xfree86.org/) and its contributors", in the same place and form as other third-party acknowledgments. Alternately, this acknowledgment may appear in the software itself, in the same form and location as other such third-party acknowledgments.

The MIT License is similar to the 3-clause "modified" BSD license, except that the BSD license contains a notice prohibiting the use of the name of the copyright holder in promotion. This is sometimes present in versions of the MIT License, as noted above.

The original BSD license also includes a clause requiring all advertising of the software to display a notice crediting its authors. This "advertising clause" (since disavowed by UC Berkeley^[6]) is only present in the modified MIT License used by XFree86.

The MIT License states more explicitly the rights given to the end-user, including the right to use, copy, modify, merge, publish, distribute, sublicense, and/or sell the software.

A 2-clause BSD-style license, found in software such as Apple Inc.'s WebCore (though most of WebCore is under the LGPL) is essentially identical to the MIT License, as it does not contain an advertising clause.

The University of Illinois/NCSA Open Source License combines text from both the MIT and BSD licenses; the license grant and disclaimer are taken from the MIT License.

• List of software that uses the MIT License

• The MIT License template
• The X Window System Trap by Richard Stallman.