However, someone could make a change, redistribute under the same term, and then someone else could undo the change, and redistribute, essentially redistributing the original without modification.
They did not "reassign the meaning". They created the term, it did not exist before their usage. They created it to mean the thing you're now saying it doesn't mean.
There's terms that if you attempt to use the literal meaning of the component words, you'll confuse people. This is one. It's like a trademark or an idiom, it has extra meaning beyond the literal due to cultural association.
> Not gonna argue or flamebait though, please just tell the correct term for projects with open source but non-free-software license and I’ll be happy to use it from now on.
I've seen "source available" used and that always seemed fine to me.
OSI/FSF decided to use generic words as label to promote their specific ideas. The ambiguity of that unspecific wording choice is on them, not on the rest of the world.
Just because "gravy boat" has the word boat in it does not mean it is actually a real boat. "Whisky on the rocks" has ice in it, not actual rocks.
Free Software and Open Source Software have widely agreed upon meanings, and just because you think intuitively it would make more sense for "whisky on the rocks" to be served over actual rocks doesn't mean you're better at understanding english words than the rest of us.
Who is “we”?
My point is that I don’t think that your premise of “collective agreement” is true for “open source” or “free software”. I don’t agree with it, and I know a bunch of other people that don’t do either.
Language is cultural and context-specific. Not everyone has to agree, but if you talk to software people about "open source" and don't mean what everybody else means, you're just going to confuse and annoy people instead of communicating.
Language is not set in stone either, and the perception of what terms mean may change over time, even within one and the same cultural context. That’s why we are having debates and discussions. The world of computer people is no exception of this phenomenon – the etymology of the word “computer” is a literal example for that.
Open Source, as defined by the Free Software Foundation or Open Source Initiative, requires the right to create a modified version of a piece of software and sell it. It doesn't matter if the modification is nothing.
A trademark on the name will require a reseller to rename it to avoid trademark infringement.
A patent on some part of it is a scummy way to do it, but that violates the spirit of open source.