| Author | Massachusetts Institute of Technology |
|---|---|
| Publisher | Massachusetts Institute of Technology |
| Published | 1988 |
| DFSG compatible | Yes |
| Free software | Yes |
| OSI approved | Yes |
| GPL compatible | Yes |
| Copyleft | No |
| Copyfree | Yes[1] |
| 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 provided all copies of the licensed software include a copy of the MIT License terms. Such proprietary software retains its proprietary nature even though it incorporates software under the MIT License. The license is also GPL-compatible, meaning that the GPL permits combination and redistribution with software that uses the MIT License.
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Since MIT has used many licenses for software, "MIT License" is viewed as ambiguous by the FSF and thus consider the names "Expat license" (used for the Expat)[2] and the "X11 license" (also called "MIT/X Consortium License"; used for the X Window System by the MIT X Consortium) to be more accurate.[3] The "MIT License" often used and published on the official site of Open Source Initiative[4] is the same as the Expat license.
Comparing to the Expat license,[2] X11 license[3] and the "MIT License" used for ncurses by the Free Software Foundation in 1998[5] adds this clause:
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 clause that requires attribution in software documentation, like the original 4-clause BSD license.[6] The Free Software Foundation contends that this addition is incompatible with the version 2 of the GPL, but compatible with version 3:[7]
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. Alternatively, this acknowledgment may appear in the software itself, in the same form and location as other such third-party acknowledgments.
Software packages that use one of the versions of the MIT License include Expat, PuTTY, the Mono development platform class libraries, Ruby on Rails, Lua (from version 5.0 onwards), and the X Window System, for which the license was written.
A common form of the MIT license (the same version as the Expat license, not identical with the X sources) is defined as follows:[4]
Copyright (C) <year> <copyright holders> 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 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[8]) is 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 used by FreeBSD (and preferred for NetBSD) is essentially identical to the MIT License, as it contains neither an advertising clause, nor a prohibition on promotional use of the copyright holder's name.
Also similar in terms is the ISC license, which has a simpler language.
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.