License

SFML libraries

SFML is completely free for any use, commercial or not, open-source or not. That is, you can use SFML API in your project without any restriction.
Indication that you use SFML in your project is not required, but would be appreciated.

Source code is provided under the terms of the zlib/png license : 

SFML - Copyright (c) 2007-2008 Laurent Gomila

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.

External libraries used by SFML