Zlib/libpng License

The zlib/libpng License is a GNU General Public License compatible free-software license.

It is used by the zlib compression library, and various other free software projects.

License text
Copyright (c) This software is provided 'as-is', without any express or implied warranty. In no event will the authors 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.