It might seem clear to those of us who’ve heard the whole story, but free speech isn’t a great analogy at all, which means this will always require a lengthy explanation to someone new to the concept. Free speech is a constitutionally protected right in the US (and something else in other countries) that comes with a list of limitations and exceptions, while “free software” is not in general a legally protected right, and in GNU’s implementation requires a viral license that eliminates some kinds of freedom, e.g., it’s specifically and explicitly not public domain. It’s fine to clarify that “free” doesn’t mean money in this case, but that’s hardly a clear explanation of what it does mean.