LICENCE.txt

PNG Reference Library License version 2
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 * Copyright (c) 2019 PyCrunch.

The software is supplied "as is", without warranty of any kind,
express or implied, including, without limitation, the warranties
of merchantability, fitness for a particular purpose, title, and
non-infringement.  In no event shall the Copyright owners, or
anyone distributing the software, be liable for any damages or
other liability, whether in contract, tort or otherwise, arising
from, out of, or in connection with the software, or the use or
other dealings in the software, even if advised of the possibility
of such damage.

Permission is hereby granted to use, copy, modify, and distribute
this software, or portions hereof, for any purpose, without fee,
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 or parts of it in a product, an acknowledgment in the product
    documentation is appreciated. This only applies to open-source software. You cannot use this product, code, or parts of it, in commercial products, including, but not limited to free products with ads, trial versions. 
    You must ask PyCrunch team for permissions and clearly describe use-cases, if you plan to embed this engine, or parts of it into commercial product.

 2. Altered source versions must be plainly marked as such, and must
    not be misrepresented as being the original software.

 3. This Copyright notice may not be removed or altered from any
    source or altered source distribution.