Extracted from pigz.c
--- /dev/null	2020-07-04 07:25:57.571395009 +0200
+++ ./LICENSE	2020-07-06 10:41:59.471408894 +0200
@@ -0,0 +1,20 @@
+Copyright (C) 2007-2017 Mark Adler
+
+This software is provided 'as-is', without any express or implied
+warranty.  In no event will the author be held liable for any damages
+arising from the use of this software.
+
+Permission is granted to anyone to use this software for any purpose,
+including commercial applications, and to alter it and redistribute it
+freely, subject to the following restrictions:
+
+1. The origin of this software must not be misrepresented; you must not
+   claim that you wrote the original software. If you use this software
+   in a product, an acknowledgment in the product documentation would be
+   appreciated but is not required.
+2. Altered source versions must be plainly marked as such, and must not be
+   misrepresented as being the original software.
+3. This notice may not be removed or altered from any source distribution.
+
+Mark Adler
+madler@alumni.caltech.edu