This appears to be most simple.
The remaining question: How to handle the year of the copyright notice?
All rights reserved.
Definition: The "authors of nmh" includes anyone, past or present, who has
-worked on the nmh source code.
+worked on the nmh source code. The "nmh source code" includes the source
+code of mmh (meillo's mail handler).
Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met: