update copying

COPYING

@@ -15,3 +15,16 @@ terms of that license as well.
 Stellar Development Foundation may, at the foundation's option,
 relicense any version of this software under any license the
 foundation sees fit.
+
+
+If you took CS244b from David Mazieres at Stanford and received credit
+for the class, you may at your option re-license this software under
+the Apache 2.0 license available at the following URL:
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+To relicense the software, you must change this COPYING file to add a
+line of the form "Relicensed by YOURNAME under Apache 2.0 on DATE"
+(substituting YOURNAME and DATE as appropriate).  The Apache 2.0
+license lets you incorporate this software into proprietary systems,
+but only if you have taken CS244b (or hired someone who took CS244b).