Open Source has a -legal- meaning - in the sense that Open Source Licenses are legal documents which specifically cover what can and can't be done.
Unfortunately the legal system does not just evolve terminology to suit whatever the current venicular is.
>> a) whether we can disambiguate between "public source"
The common phrase for this is "source available"
>> by irately pointing the discrepancy out we only come out as pedantic
When we allow words to change, when we allow misinterpretations of those words to proliferate, then we need to accept we are giving up the very freedoms those words set out to mean. If we just accept a new definition of Open Source today, then what's to stop the next generation of people/companies redefining it again in 10 years time? What happens when we start (colloquially) using the phrase to mean "the source is open inside the company, but not available outside it."
Unfortunately we see this language evolution around us all the time. "Free Speech" doesn't mean what most people think it means. Neither does "Constitutional Right". And evidently there's a group of technologists, or would-be-technologists (never mind joe public) who do not understand what Open Source means.
To you, defending the term becomes pedantry. But you live in a world where you have the access to code that you do, precisely because the older generation stood up for the specifics of the term - and fought for the very freedoms you now enjoy. You describe the corrections as "technically correct" without perhaps understanding the magnitude of effort that has gone into making it what it is.
So forgive us please if we hold tightly to what was so hard won.
Perhaps, and I mean this sincerely, rather than co-opting the past to suit your current needs, it's time for the current generation to fight for the ideals that -you- believe in. Just please, don't co-opt our hard-won terminology to do so.