Not entirely true: some people will change with smaller warnings, even just this news. Others require graphic warnings plastered on the front to change. More warnings, more impact.
Low end: “you can see the source but can’t do anything with it” (questionable whether this counts as open source at all)
High end “do what you want, it’s literally yours” (public domain).
One can debate where the low boundary of “open source” is, or what makes one license more or less free than another, but the spectrum is the range of limitations.
That’s not a problem with middle click paste, that’s a problem with Firefox. If you hit ctrl+v in Firefox does it search for whatever is in your clipboard? No, so why should it do that when you paste by mouse click?
He needs to go there personally to break ground though.