The world of licenses: deal with MIT license

    In previous articles, I tried to talk about the GPL and BSD licenses , their history, types and how they differ from each other. This time I will try to consider another, slightly less popular license - X11 (MIT) license.

    X11 (MIT) license

    The history of this license begins in 1984, when the idea of ​​creating a graphic subsystem called “X” arose in the computer science laboratory of the Massachusetts Institute of Technology. The name came about as the name of a follower of a similar “W” system used for the “V” operating system. In the English alphabet, as you know, “X” follows “W”. The first release of X1 was the first truly independent graphics hardware.

    Development progressed rapidly and in early 1985, the X6 was released. It seems that the license under which this version was released was not free, because the product was distributed to interested groups of developers for money. However, X9 was already released in September 1985 under a free license, which later began to be called the MIT license (MIT license). Later, the version number in the product name grew to 11 and the system began to develop as X11 (released in September 1987). By this time, the institute had ceded the rights to the system of the specially created organization X Consortium, Inc. After that, all versions of the product became known as “X11”, and its releases began to be named differently, starting with X11R2 (released in January 1988) and X11R7.3 (released in September 2007). True, not all versions were released by the X Consortium, as this organization disbanded in 1996 and the project's banner was first raised by The Open Group (1997), which eventually formed the X.Org Foundation in 2004. But this is another story that deserves a separate article.

    What does the X11 license contain ? It practically repeats the license of 2 BSD clauses (FreeBSD license), only lists more detailed permissions instead of “Redistribution and use are allowed, both in source code and in binary form, with or without modification” MIT license says the following (mine translation): “This permission is given free of charge, to any person who receives a copy of this software and related documentation to use the software without prohibitions, without restrictions on the rights to use, copy, modify, combine, publish, distribute wounding, sublicensing, and / or selling copies of the software and permits those who are provided with the software to do so. ”. It is noticeable that the X11 license is more verbose, besides it does not contain an enumeration of points, who knows, maybe this also served as the fact that the license gained considerable popularity. I must say that the original version of the X11 license, among other things, also contained a ban on the use without permission of the name X Consortium in advertising and other materials used to promote its software. In this, it looked like a license of 3 BSD points.

    The "final" version of the license in the form in which it is now distributed, the license received in the form of the so-called Expat license . This option differs only in that it does not offer X Consortium.

    Obviously, in a large organization like MIT, there is more than one license. Below I would like to give the results of my research in the field of what other licenses exist from the Massachusetts Institute of Technology:

    As you can see, licenses from MIT do not end with the simplest one, therefore, it is historically more correct to call the MIT license either X11 or Expat. But in our time, a large cohort of software has already been formed that is released under a license, which the software authors themselves called MIT. Today, many developers and organizations (including the Open Source Initiative ) do not distinguish between X11, Expat, and MIT licenses, calling all licenses one common term “MIT license”.

    In general, the MIT license allows you to freely use someone else's work. In the event that you will distribute your product in which there will be other people's codes licensed under the MIT license, you are required to indicate the copyrights of the authors of the codes, the license text and disclaimer. In fact, you should duplicate the text of the license you received in your product. The MIT license is not a copyleft license, that is, it does not require the product you will distribute to be open, you can use any codes under the MIT license in any of your open or closed projects.

    It should also be noted that the MIT license is compatible with the GPL. That is, you can release a product under the GPL, part of which will be code with a MIT license.

    XFree86 license v1.1

    In the context of the MIT license, it’s worth a little talk about the XFree86 v1.1 license. XFree86 is a variant of X Window that was designed for UNIX systems running IBM PC-compatible computers in the early stages. Initially, this product was distributed under the MIT license, and only in 2004 the license was changed . The changes were serious: 4 points appeared, the emphasis on the requirements for the mandatory indication of copyrights in binary and source codes and the mandatory indication of a certain line in the documentation for the software. The last moment related to the documentation made this license incompatible with GPLv2, at that time the latest version of the GPL. GPL compatibility was brought only by the GPLv3 released in 2007. XFree86 license v1.1 is considered compatible with this version.


    [1] X11
    [2] XFree86

    PS: if you find inaccuracies or errors in the article, please let me know in the comments or by email

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