Another in my series of highlighting various public domain dedications. This time, MD5:
MD5 (md5.cpp and md5.h)
This code implements the MD5 message-digest algorithm. The algorithm is due to Ron Rivest. This code was written by Colin Plumb in 1993, no copyright is claimed.
This code is in the public domain; do with it what you wish.
Mathematical formulae generally aren’t copyrightable, so insomuch as this is solely an algorithm and not code implementing that algorithm, copyright wouldn’t subsist in the first place. So in the case of the Rivest algorithm mentioned, it’s good to know that copyright isn’t being claimed over it despite the chances of it existing are pretty close to nil.
For the code however, it could very well have copyright. Copyright is automatic — you don’t have to apply for a copyright in order to have one. Copyright “flows from the pen to the paper”, as they say (or in this case from the fingertips to the keyboard). Since copyright subsists, I think more accurate drafting would be to say that “copyright is waived”.
In either event, the MD5 text gives a clear intent to give up all copyright, and if the copyright couldn’t be technically waived on the basis of this for some reason, then I would think a court would read in a very very broad license in its place.