In one sense, I feel "The Open Source Movement" have co-opted a plain english two word phrase.
Their introduction there can be rewritten as "Open source doesn't just mean the source is open. We claim there are also implications about the means of distribution."
It's as though someone was telling people "free beer" doesn't just mean beer that's free, it also needs to be in glass not cans - free beer in cans needs to be called something else…
I think there's a lot of "open source" software out there that is not "open source(tm)". I'm not sure "the open source movement" are doing themselves any favors by aggressively defending their particular definition of a descriptive phrase that is widely known and easy to assume you understand.
(But I also understand the need for specific technical meanings in the software field, and that phrases like "open source" end up being part of the field's jargon, and have far more specific technical meanings than the "plain english" deconstruction of the words indicate. I just think the "open source" case has backed itself into a corner where people assume a plain english interpretation of the phrase, then have the "open source movement" people need to jump on them and say "no, you're wrong". As displayed upthread.)