Freedom is such a vague word, we shouldn’t use this word if we want to be precise about what we mean by it.
When we talk about free software, we point to transparency, studyability, tinkerability and sharability. The openness to allow ourselves to use our tools with freedom.
However, I do not think we should use the term open source. The reason for my distancing of the word source is because the word makes us think about development instead of the end user. Because if we want these kinds of software to appeal to the masses, we the word to emphasize that it is meant for them. Instead, I would use the term open software, open tool or open machine.
Things like the MS-PL strike me as Open Source but not Free Software, but I can’t think of a contrary example which is Free Software but not Open Source.
I read a Stack Overflow discussion about it a few years ago and if I remember correctly, they found some obscure one which was free but not open source.
Though I don’t remember which one it was.