Looking at the header of the various .cpp and .h files, you will see
the following boiler plate:

 * PROPRIETARY INFORMATION.  This software is proprietary to POWDER
 * Development, and is not to be reproduced, transmitted, or disclosed
 * in any way without written permission.

This would seem to prohibit all use or distribution of this source.
So, how on earth did you get a copy?

The answer is that the author (Jeff Lait) decided to extend a sort of
written permission over the source code.

So, the million dollar question, which license?

-------------------------
This work is licensed under the Creative Commons Sampling Plus 1.0
License. To view a copy of this license, visit
http://creativecommons.org/licenses/sampling+/1.0/ or send a letter to
Creative Commons, 171 Second Street, Suite 300, San Francisco,
California, 94105, USA.
-------------------------

(This, obviously, does not apply to files which state other licenses,
for example, mt19937ar.c is separately licensed.  Note, in particular,
the bitmaps are under a different license(s) that you can find in the
relevant artpacks)

Now, what does Sampling Plus entail?

1) This is *NOT* an Open Source license.  This code is not "free".

2) You can redistribute the UNCHANGED source non-commercially.

3) You can modify the source to port to other platform or get it to
   compile on your system. ("The above rights include the right to
   make such modifications as are technically necessary to exercise
   the rights in other media and formats.")  You may also publish the
   resulting changes to the source.
   a) You are not required to publish the changes, but I encourage you
      to provide them to me to roll into the main POWDER baseline.

4) You may *NOT* "fork" the POWDER distribution.  But...
   a) You can extract "samples" from the distribution.  These samples
      can be used commercially.  The samples must not constitute a
      substantial part of your new work.  For example, you could lift
      the Line of Sight routines for your roguelike and merge it into
      whatever new license you wish.
   b) You can "mash up" the code.  Think "total conversion" - a result
      which a player would not recognize the similarities to POWDER.

The sampling license, you will note, is designed for music, not code.
This leaves open some questions of interpretation which I shall
interpret here:

1) Warranties.  This code is not executable hence requires no more a
   warranty than the science fiction novel I just read.  The compiler
   of the code is responsible for disclaiming warranties in the
   resulting executable.  This is likely *you*.  So, if you are
   paranoid, read the damn source.

2) The result of sending the source through the compiler is a derived
   work, but *not* a "highly transformative" work.  The purpose of the
   re-creativity is for there to be an injection of creativity in the
   process which, barring AI, we shall claim the computer does not
   possess.

3) If you want to get all rules-lawyersy and what-not about the
   specifics of what this means, you have two options:
   a) Contact me (Jeff Lait) regarding your specific application and I
      will try and find someway to approve it.
   b) Treat this whole license as invalidly formed and hence reverting
      to a standard all-rights-reserved distribution.  In which case I
      ask you to please immediately delete your unauthorized copy of
      the source.  HTH.  HAND.

Finally, a note about patches.   I understand it is commonly
understood that patches submitted to the creator are implied to be
under the creator's license.  In this case, I shall consider such
patches to be "samples".  As such, I will be able to incorprate them
burdened only by the need to attribute the patch creator.  I will
retain the right to re-license the resulting work under another
license, either stricter (ie, stop distributing source) or weaker (ie,
public domain (if that is even possible, sigh) or GPL)
