I don't want to sound unfriendly, but I consider "about" as a serious mistake.
Yes. And no.
Talking "about" Free Software is what we do the whole time.
True. Therefore it's not a mistake. It's a mistake if you want to talk about the term, but the document doesn't talk about the term alone. It explains why we speak about Free Software (instead of speaking about open source or about computers or about linux). Actually is explains "why we speak about Free Software".
That said, I'm not sure if "speak" or "talk" is better, but I'm not a native speaker, I think MJ Ray would have complained if it's wrong.
/alessandro