The english language is full of ambiguity if you choose to be pedantic, yet somehow most people manage to communicate.
The fact that you knew I was referring to rust's license means my English was in fact not undefined, but exactly as clearly defined as one can hope english to be, i.e. we both thought it meant the same thing.
In my opinion, in context, "free software license" is also a clear and common phrase, not undefined behavior.
Essentially, I think everyone has agreed that "free software", unless you add more qualifiers, will refer to the FSF definition of free software https://www.gnu.org/philosophy/free-sw.html
The fact that you knew I was referring to rust's license means my English was in fact not undefined, but exactly as clearly defined as one can hope english to be, i.e. we both thought it meant the same thing.
In my opinion, in context, "free software license" is also a clear and common phrase, not undefined behavior.
Essentially, I think everyone has agreed that "free software", unless you add more qualifiers, will refer to the FSF definition of free software https://www.gnu.org/philosophy/free-sw.html
The FSFs definition includes both the licenses rust is licensed under: https://www.gnu.org/licenses/license-list.html#Expat
The FSF would happily call BSD, MIT, and Apache "Free Software Licenses", and in fact do so.