licenses: Update no-source-code license note.

Bug: 615456

licenses/no-source-code

@@ -6,8 +6,10 @@ Free Cultural Works [3], even if it is distributed under a free
 software license. Source code is the preferred form in which a
 programmer would modify the work.
 
-The "no-source-code" license label must never be used on its own, but
-only along with the license under which the package is distributed.
+Note to developers: The "no-source-code" license label must never be
+used on its own, but only along with the license under which the
+package is distributed. It should only be used together with licenses
+that would qualify as free when used for source code.
 
 [1] http://www.gnu.org/philosophy/free-sw.html
 [2] http://opensource.org/osd