xref: /third_party/libjpeg-turbo/LICENSE.md

libjpeg-turbo Licenses
======================

libjpeg-turbo is covered by three compatible BSD-style open source licenses:

- The IJG (Independent JPEG Group) License, which is listed in
  [README.ijg](README.ijg)

  This license applies to the libjpeg API library and associated programs
  (any code inherited from libjpeg, and any modifications to that code.)

- The Modified (3-clause) BSD License, which is listed below

  This license covers the TurboJPEG API library and associated programs, as
  well as the build system.

- The [zlib License](https://opensource.org/licenses/Zlib)

  This license is a subset of the other two, and it covers the libjpeg-turbo
  SIMD extensions.


Complying with the libjpeg-turbo Licenses
=========================================

This section provides a roll-up of the libjpeg-turbo licensing terms, to the
best of our understanding.

1.  If you are distributing a modified version of the libjpeg-turbo source,
    then:

    1.  You cannot alter or remove any existing copyright or license notices
        from the source.

        **Origin**
        - Clause 1 of the IJG License
        - Clause 1 of the Modified BSD License
        - Clauses 1 and 3 of the zlib License

    2.  You must add your own copyright notice to the header of each source
        file you modified, so others can tell that you modified that file (if
        there is not an existing copyright header in that file, then you can
        simply add a notice stating that you modified the file.)

        **Origin**
        - Clause 1 of the IJG License
        - Clause 2 of the zlib License

    3.  You must include the IJG README file, and you must not alter any of the
        copyright or license text in that file.

        **Origin**
        - Clause 1 of the IJG License

2.  If you are distributing only libjpeg-turbo binaries without the source, or
    if you are distributing an application that statically links with
    libjpeg-turbo, then:

    1.  Your product documentation must include a message stating:

        This software is based in part on the work of the Independent JPEG
        Group.

        **Origin**
        - Clause 2 of the IJG license

    2.  If your binary distribution includes or uses the TurboJPEG API, then
        your product documentation must include the text of the Modified BSD
        License (see below.)

        **Origin**
        - Clause 2 of the Modified BSD License

3.  You cannot use the name of the IJG or The libjpeg-turbo Project or the
    contributors thereof in advertising, publicity, etc.

    **Origin**
    - IJG License
    - Clause 3 of the Modified BSD License

4.  The IJG and The libjpeg-turbo Project do not warrant libjpeg-turbo to be
    free of defects, nor do we accept any liability for undesirable
    consequences resulting from your use of the software.

    **Origin**
    - IJG License
    - Modified BSD License
    - zlib License


The Modified (3-clause) BSD License
===================================

Copyright (C)2009-2021 D. R. Commander.  All Rights Reserved.<br>
Copyright (C)2015 Viktor Szathmáry.  All Rights Reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

- Redistributions of source code must retain the above copyright notice,
  this list of conditions and the following disclaimer.
- Redistributions in binary form must reproduce the above copyright notice,
  this list of conditions and the following disclaimer in the documentation
  and/or other materials provided with the distribution.
- Neither the name of the libjpeg-turbo Project nor the names of its
  contributors may be used to endorse or promote products derived from this
  software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS",
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.


Why Three Licenses?
===================

The zlib License could have been used instead of the Modified (3-clause) BSD
License, and since the IJG License effectively subsumes the distribution
conditions of the zlib License, this would have effectively placed
libjpeg-turbo binary distributions under the IJG License.  However, the IJG
License specifically refers to the Independent JPEG Group and does not extend
attribution and endorsement protections to other entities.  Thus, it was
desirable to choose a license that granted us the same protections for new code
that were granted to the IJG for code derived from their software.