‡ In "Through the Looking Glass" Humpty Dumpty asserts that "When I use a word, it means just what I choose it to mean—neither more nor less".
So it matters whether it's, say, one pundit who thinks "Source code available to certain parties under license" (e.g. Microsoft Windows has been handled this way in the past) counts as Open Source, or so common that you can find dozens of erroneous examples in every major software publication of the last five years.
People writing "free reign" when they mean "free rein" might be unsalvageable at this point, whereas people saying "backslash" when they mean a forward slash - probably we can still say those people are just wrong and need to sort it out.
The vast majority of the software industry uses "open source" correctly. A small minority of people and companies with a vested interest in sowing confusion to promote their "source available" business models misuses the term and creates FUD.
The point is the adjective is commonly used imprecisely, despite a minority’s desire for it to be only used to describe a precise circumstance.
Genie, meet bottle.