"Public Domain" is a legal term, meaning that all the potential rights handed by copyright have been surrendered. Since we retain one of the basic rights of Copyright law (to be known as the author) it is important that noone incorrectly state the legal position of the source code. Under Copyright law, we could attempt to stop them from handing it out to their users in the future (I've had some fun and checked into what rights a Copyright owner has in that regard).
Actually, with OpenSSH the legal situation is somewhat more complicated since there are still some small bits of code from different authors with very slight variations in how they state that they retain that "be known as the author" right. But anyways, any vendor who mis-states the Copyright status of a piece of software should be told to fix it immediately. Keep the pressure up on these companies. Doing so is "good work".
