The word “open” is overloaded. In the domain of standardisers, a process that permits any company to participate (even if doing so is punitively expensive) is considered “open” and the resulting deliverable is considered an “open standard” even if you have to pay to read it and negotiate patent licenses to implement it.
In the domain of software and APIs, it is the deliverable that has to be open – usable for any purpose without negotiation with its rights-holders. This overloading of the term is the origin of many of today’s issues, since – properly understood – Open Source and open standards are conceptually orthogonal.
This variation in how “open” is understood within linked and overlapping domains is why “Open Source” is treated as a term of art with a consensually-agreed meaning in the domain of technology – a noun – and not as a descriptive adverbial phrase. If you see a hyphen in the middle of open-source it’s about military/political intelligence and not technology.