Update README, clarify licensing situation

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 44 insertions, 0 deletions

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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`, `include/sqfs`
+and `include/util`.
+
+The rest of squashfs-tools-ng is released under the terms and conditions of
+the **GNU General Public License version 3 or later**.
+
+Copies of the licenses 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. 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.
+
+# 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 liceses.
+
+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 zlib compression library. Copyright Jean-loup Gailly and Mark Adler.
+   This is released under the terms and conditions of the zlib license,
+   included in `licenses/zlib.txt`
+ - The zstd compression library. Copyright Facebook, Inc. All rights reserved.
+   This is released under a BSD style license, included in `licenses/zstd.txt`.