License

SFML Libraries

The SFML libraries and source code are distributed under the zlib/png license. 

SFML (Simple and Fast Multimedia Library) - Copyright (c) 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.

In short, SFML is free for any use (commercial or personal, proprietary or open-source). You can use SFML in your project without any restriction. You can even omit to mention that you use SFML -- although it would be appreciated.

External Libraries used by SFML