"Free" being the confusing word here, because it has two meanings, and often are used without context in open source software.
Typically, OSS is both definitions at the same time - free monetarily, and "free" as in "freedom" to use. JSON is an interesting case of "free" monetarily but not totally "free for use".
That is expressly the opposite goal of open source. If you arbitrarily say foo user cannot use your software, then it is NOT open source. That's more like source-available.
Nobody would continue to use linux if they randomly banned people from using it, regardless of the reason.
[side note] This is why I despise the term "open source". It obscures the important part of user freedom. The term "Free/libre software" is not perfect, but it doesn't obscure this.
