put all README.md files under CC BY-SA 4.0 License

This will make is easier for others to share README.md
files while requiring them to attribute the file
when using it.

2000/anderson/README.md

@@ -87,3 +87,12 @@ data.  Again, if it's OK with K&R, it's OK with me.
 This program is a great teaching tool for learning the semaphore code;
 and if you don't have any flags handy you can just use two copies of the
 source file.
+
+## Copyright and CC BY-SA 4.0 License:
+
+This file is Copyright (c) 2023 by Landon Curt Noll.  All Rights Reserved.
+You are free to share and adapt this file under the terms this license:
+
+    Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
+
+For more information, see: https://creativecommons.org/licenses/by-sa/4.0/