irrlicht_license.txt

The license of the Irrlicht Engine is based on the zlib/libpng license.
  Even though this license does not require you to mention that you are
  using the Irrlicht Engine in your product, an acknowledgement
  would be highly appreciated.

  Please note that the Irrlicht Engine is based in part on the work of
  the Independent JPEG Group, the zlib, and libpng. This means that if you use
  the Irrlicht Engine in your product, you must acknowledge somewhere
  in your documentation that you've used the IJG code and libpng. It would
  also be nice to mention that you use the Irrlicht Engine and the zlib.
  See the README files in the jpeglib and the zlib for
  further informations.


  The Irrlicht Engine License
  ===========================

  Copyright (C) 2002-2012 Nikolaus Gebhardt

  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 acknowledgement in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be clearly 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.