explicit license

endmatter/index.md

@@ -19,7 +19,10 @@ welcome feedback there.
 copying
 -------
 
-I may eventually dedicate this thing to the public domain, but for the time
-being please feel free to use it under the terms of Creative Commons BY-SA
-(Attribution / Share-Alike), whatever the latest version is.  I promise I will
-not license it under more restrictive terms than that.
+This work is licensed under a
+<a rel="license" href="https://creativecommons.org/licenses/by-sa/4.0/">Creative
+Commons Attribution-ShareAlike 4.0 International License</a>.
+
+<a rel="license" href="https://creativecommons.org/licenses/by-sa/4.0/">
+<img alt="Creative Commons License" src="images/by-sa-4.png" />
+</a>

index.html

@@ -3041,11 +3041,11 @@ April  5 2015
 
 
 <pre><code>$ seq 1 5 | shuf
+4
 5
 1
-2
-4
 3
+2
 </code></pre>
 
 <!-- end -->
@@ -3140,10 +3140,13 @@ welcome feedback there.
 
 <h2><a name=copying href=#copying>#</a> copying</h2>
 
-<p>I may eventually dedicate this thing to the public domain, but for the time
-being please feel free to use it under the terms of Creative Commons BY-SA
-(Attribution / Share-Alike), whatever the latest version is.  I promise I will
-not license it under more restrictive terms than that.</p>
+<p>This work is licensed under a
+<a rel="license" href="https://creativecommons.org/licenses/by-sa/4.0/">Creative
+Commons Attribution-ShareAlike 4.0 International License</a>.</p>
+
+<p><a rel="license" href="https://creativecommons.org/licenses/by-sa/4.0/">
+<img alt="Creative Commons License" src="images/by-sa-4.png" />
+</a></p>
 
 <hr />
 <script>

introduction/index.md

@@ -13,7 +13,6 @@ most of the time.  I still get some stuff done.
 
 This is a work in progress.  It probably gets some stuff wrong.
 
-
 -- bpb / [p1k3](https://p1k3.com) / [@brennen](https://twitter.com/brennen)
 
 <div class=details>