Add README with license update

README

@@ -0,0 +1,21 @@
+Discussion of Compilers: Principles, Techniques, and Tools
+==========================================================
+
+This repository is an archive of a 2013 work exploring selected exercises
+from the "Dragon" book, a canonical text on compiler construction.
+
+Please note that this book is non-free, which is in my strong opinion
+inappropriate for the dissemination of knowledge.  It is otherwise a good
+text.
+
+
+Building
+--------
+Simply run `make'.
+
+
+License
+-------
+Licensed under the Creative Commons Attribution-ShareAlike 4.0 International
+License.
+

s428.tex

@@ -1,7 +1,7 @@
-% Copyright (C) 2013 Mike Gerwitz
+% Copyright (C) 2013, 2018 Mike Gerwitz
 %
-%   Licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported
-%   License.
+%   Licensed under a Creative Commons Attribution-ShareAlike 4.0
+%   International License.
 %
 % Discussion of section 4.2.8 (exercises for section 4.2) in CPTT (the
 % "dragon book")
@@ -843,4 +843,14 @@ excellent segue into proving more sophisticated grammars. Of course, the reader
 can surely see the challenges that might arise from attempting to prove much
 more complicated grammars. \exend
 
+
+\section{License}
+This work is licensed under the Creative Commons Attribution-ShareAlike 4.0
+International License---you are free to use, share, and modify it to suit
+your needs, provided that you give proper attribution and license derivative
+works under similar terms.  For more information, see:
+
+\tt{https://creativecommons.org/licenses/by-sa/4.0/}.
+
 \end{document}
+