The "we" that gets to do the undoing *today* is everyone that has a license to have a copy of your program. I used "us" expansively and assumed that most people are potentially in the set of people who could have a license to whatever software it was you were mentioning. The "us" and "we" of public domain is everyone, period. Of course, all of this is really from my context as a USian. Most-to-many people here aren't actually present in the US and their own legal requirements are probably entirely different.