The OSI are the people who made it up, and the only reason why anybody cares about it. If you call yourself Open Source and you don't comply with the OSI definition, you're a parasite trying to commit fraud with the good will generated by other people.
I also don't care if somebody in 1975 said "I like to be open, and I'll let anyone look at the source." Old McDonald had a farm before McDonald's was a restaurant, but that doesn't mean that if you open a restaurant called McDonald's that is decorated like a McDonald's, you're not a scammer. I know your plastic fruit is carbon-based, but if you label it as "organic" you're a thief.
If you're not trying to scam people, be creative and make up your own catchphrase for letting people look at your source code - or don't even, because the whole idea of having a branding for allowing people access (and rights to) the source is imitation of the FSF and OSI.
I'm ok with saying that Open Source is now widely understood to mean what the OSI says, that's just a function of how language evolves. But we don't need to re-write history to get there.
Open Source isn't a brand, it isn't a trademark, it was hijacked by OSI to enforce their specific interpretation of a phrase that was already in use. OSI wasn't founded until 1998, over a decade after the term open source software became popular and was used throughout the unix and linux communities and in businesses such as Caldera. Before OSI came up with the OSD many creators of open source software had non-compete clauses in the licence.
"Open Source software" was never a popular term before the OSI promoted it. "Open Source software" is a reworking of the original term "Free software" to be more palatable to businesses. The Open Source Definition is very similar to the older Free Software Definition and virtually all software qualifies as either both or neither.
Likewise I feel like it only became "the common understanding" due to pushing within the past decade. Before that "the common understanding" was what people are only now calling "source available" - which I don't think I'd heard of before just a couple years ago.
Many countries have false advertisement laws, so if you say something is open source, it does mean various things. So, if you sell the product for free, then of that free product the source has to be practically available.
No, "Open source" had been used as a term for many decades before the February 3rd, 1998 meeting where Christine Peterson suggested that it be borrowed to describe software. This is much of the reason why any attempts to trademark the phrase have been denied.
OSI was financed by Tim O’Reilly originally and now by big tech companies as a way to co-opt th free software movement and make it more business friendly.
They have successfully convinced a generation of developers that “Open Source” is pure and holy, but a licensee that includes a term that says something like no company making more than $100 million per year can use this software for free is unclean and maybe even evil.
They don’t want alternative licenses to exist because it hurts their bottom line.
I also don't care if somebody in 1975 said "I like to be open, and I'll let anyone look at the source." Old McDonald had a farm before McDonald's was a restaurant, but that doesn't mean that if you open a restaurant called McDonald's that is decorated like a McDonald's, you're not a scammer. I know your plastic fruit is carbon-based, but if you label it as "organic" you're a thief.
If you're not trying to scam people, be creative and make up your own catchphrase for letting people look at your source code - or don't even, because the whole idea of having a branding for allowing people access (and rights to) the source is imitation of the FSF and OSI.