So you simply mean "not being coerced"?
As when a AI performs an action itself has calculated without having to follow some other agents decision of what it should do?
I mean what the usual expression I mentioned means.
It is closely related to lack of coercion for sure, but it's very difficult to give definitions that capture the full meaning of common expressions (dictionaries usually approach the meaning, but fail to capture it), especially with folk psychology concepts (including morality). It's not the same as not being coerced, since (say) I wouldn't be inclined to think a cockroach acts of its own free will (I might be mistaken, but that seems unlikely), and also there is the issue of whether one counts internal states as coercion (e.g., unjustified fear, kleptomania, etc.)
So, I'm not going to take a stance on whether "I'm writing this post of my own free will" means the same as "I'm writing this post without being coerced", since I don't know whether that is the case.
On the other hand, I do take a stance on whether I'm writing this post of my own free will - I am.
If that's not clear enough, then I'm afraid that that's the best I can do. I still disagree with Speakpigeon's claim, unless he means something else by "free will", in which case I would ask him what he means by that expression.