PERMISSIVE

  This work 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 work.

  Permission is granted to anyone to use this work for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this work must not be misrepresented; you must not
     claim that you wrote the original work. If you use this work
     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 work.
  3. This notice may not be removed or altered from any source distribution.