Add a LICENSE.

Fix #281.

Author: munificent

LICENSE

@@ -0,0 +1,105 @@
+Copyright (c) 2009 Robert Nystrom
+
+------------------------ Commentary ------------------------
+
+The licensing story for this repository is a little complex.
+Here's my motivation:
+
+* I want you to get as much use out of the material here as
+  possible. I wrote this book to help you, and I don't want
+  you to be encumbered when it comes to making the most of
+  it. That's also why I put it online for free.
+
+* I have been immensely fortunate to have a large number of
+  people contribute to the book through bug reports, fixes,
+  pull requests, and other suggestions. Putting on GitHub
+  and treating it like an open source project made a
+  dramatic improvement in the resulting quality of the
+  book.
+
+  I want to ensure people can fork the repo, send me fixes,
+  etc. without violating the license or feeling weird.
+
+* When it comes to code, I'm completely comfortable with
+  people redistributing, remixing, changing, whatever with
+  it. I've been using the MIT license for open source stuff
+  for decades.
+
+* When it comes to my prose and the visual design of the
+  site, that feels a little more, I don't know, *me* than
+  the code. The words are in my voice, and the look of the
+  site is part of its and, by extension, my brand.
+
+  I feel weird thinking about someone, say taking one of the
+  chapters and making significant changes to it to fit their
+  writing style while still having some of it read like it
+  came from me. Likewise, I'd be sad to see another site
+  online that looked exactly like mine because it reuses my
+  stylesheets.
+
+* Because -- and this came as a total surprise to me --
+  there are foreign publishers interested in the
+  translation rights to the book, I want to be careful to
+  not be so permissive that it prevents me from signing
+  typical contracts that give them exclusive translation
+  rights to certain territories and languages.
+
+* If I allow the prose to be redistributed commercially,
+  there is nothing preventing someone from slapping
+  together a cheap print or ebook version of the book and
+  putting it up for sale. I'm not too worried about my own
+  sales being undercut, but I very much want to avoid
+  readers finding themselves with a low quality book that
+  they incorrectly think is from me.
+
+  I worked very hard on this book, including type setting,
+  layout, generating the ePub file, styling it, etc. I want
+  you to get the best possible experience.
+
+All of this is way more complex than I'd like, especially
+since my brain isn't wired to care about intellectual
+property. I like thinking about making stuff, not thinking
+about the legal rights around the stuff I made. (If your
+brain is wired to think about legal stuff and you see that
+I'm doing something dumb, please do let me know.)
+
+The best solution I've been able to come up with is to use
+two licenses:
+
+------------------------ License(s) ------------------------
+
+Each file in this repository falls under one of two
+licenses. Files whose extension is ".html", ".scss", ".css",
+".markdown", or ".txt" use this Creative Commons license:
+
+    Attribution-NonCommercial-NoDerivatives 4.0
+    International (CC BY-NC-ND 4.0)
+
+    https://creativecommons.org/licenses/by-nc-nd/4.0/
+
+All other files, including (but not limited to) ".py", "h",
+and ".cpp" use the MIT license:
+
+    Permission is hereby granted, free of charge, to any
+    person obtaining a copy of this software and associated
+    documentation files (the "Software"), to deal in the
+    Software without restriction, including without
+    limitation the rights to use, copy, modify, merge,
+    publish, distribute, sublicense, and/or sell copies of
+    the Software, and to permit persons to whom the Software
+    is furnished to do so, subject to the following
+    conditions:
+
+    The above copyright notice and this permission notice
+    shall be included in all copies or substantial portions
+    of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+    ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+    TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+    PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+    SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+    CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+    OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+    IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+    DEALINGS IN THE SOFTWARE.