com/options/license/Cube

Cube game engine source code, 20 dec 2003 release.

Copyright (C) 2001-2003 Wouter van Oortmerssen.

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.

additional clause specific to Cube:

4. Source versions may not be "relicensed" under a different license without
my explicitly written permission.