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COPYING.md

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License of squashfs-tools-ng

The libsquashfs library is released under the terms and conditions of the GNU Lesser General Public License version 3 or later. This applies to all source code in the directories lib/sqfs, lib/util and include/sqfs with the following exceptions:

  • lib/util/src/xxhash.c contains a modified implementation of the xxhash32 algorithm. See licenses/xxhash.txt for copyright and licensing information (2 clause BSD license).
  • lib/util/src/hash_table.c, include/util/src/hash_table.h and lib/util/src/fast_urem_by_const.h contain a hash table implementation (MIT license). See licenses/hash_table.txt for details.

The rest of squashfs-tools-ng is released under the terms and conditions of the GNU General Public License version 3 or later, with the following exceptions:

  • lib/compat/src/fnmatch.c has been copied from Musl libc.
  • lib/compat/src/getopt.c has been copied from Musl libc.
  • lib/compat/src/getopt_long.c has been copied from Musl libc.
  • lib/compat/src/getsubopt.c has been copied from Musl libc.

The components copied from Musl libc are subejct to an MIT style license. See liceneses/musl.txt for details and only compiled into executable programs if the target system does not provide an implementation.

Some additional components of lib/compat are also LGPL licensed, to allow their inclusion in libsquashfs. See SPDX identifiers.

Copies of the LGPLv3 and GPLv3 are included in licenses/LGPLv3.txt and licenses/GPLv3.txt respectively.

The original source code of squashfs-tools-ng has been written by David Oberhollenzer in 2019 and onward. Additional contributions have been added since the initial release which makes some parts of the package subject to the copyright of the respective authors. Appropriate copyright notices and SPDX identifiers are included in the source code files.

Although the existing squashfs-tools and the Linux kernel implementation have been used for testing, the source code in this package is neither based on, nor derived from either of them.

Documentation, examples and the Build System

The auto-tools based build system has in large parts been hacked together by copy & pasting from various tutorials and other projects (mostly util-linux, and mtd-utils), overhauled many times since 2015.

The m4 macros in the m4 directory were copied verbatim and have explicit licenses. Please respect those. As for everything else, feel free to copy and paste it as you wish.

The doc directory contains measurement data, pseudo lab reports and an RFC style write-up of the SquashFS format. You may do with those as you please.

If you use those as a basis for writing about SquashFS or this package, please cite your sources and mark verbatim quotations as such. I won't be angry if you don't, but a thesis supervisor, reviewer or fellow Wikipedian might be.

The example programs in the extras directory are licensed under the 0BSD license, a copy of which can be found in licenses/0BSD.txt.

Binary Packages with 3rd Party Libraries

If this file is included in a binary release package, additional 3rd party libraries may be included, which are subject to the copyright of their respective authors and the terms and conditions of their respective licenses.

The following may be included:

  • The LZO compression library. Copyright Markus F.X.J. Oberhumer. This is released under the terms and conditions of the GNU General Public License version 2. A copy of the license is included in licenses/GPLv2.txt.
  • The LZ4 compression library. Copyright Yann Collet. This is released under a 2 clause BSD style license, included in licenses/LZ4.txt.
  • The XZ utils liblzma library is released into the public domain. An excerpt from the COPYING file of its source code archive is included in licenses/xz.txt.
  • The zstd compression library. Copyright Facebook, Inc. All rights reserved. This is released under a BSD style license, included in licenses/zstd.txt.
  • Parts of the Musl C library. Copyright Rich Felker, et al. This is released under an MIT style license, included in licenses/musl.txt.

Independent of build configurations, the libsquashfs library contains the following 3rd party source code, directly linked into the library:

  • A modified version of the xxhash32 hash function (Copyright Yann Collet). This is released under a 2-Clause BSD License. See licenses/xxhash.txt for details.
  • A hash table implementation liftet from the Mesa3D source code. This is released under the MIT/X11 license. See licenses/hash_table.txt for details.