This program is distributed under the OSI-certified zlib/libpng license.
http://www.opensource.org/licenses/zlib-license.php

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.