Accurately voicing my thoughts on this would probably go against the HN guidelines, so I'll just let this sentence from the article speak for itself:
>But our vision is a grand one—unify all of computation into a single coherent language, and for that, the FOSS development model is not well suited.
Well, good luck with that.
Wolfram in that sense is just being honest about their motivations by having it be proprietary from the get-go.
Open source does not necessitate listening to the community. Ever. Even if they were to release it under an OSS license, they could just turn off PRs. Or if it's "source available", same story.
The ones that succeed keep the community happy and either focus on adding value on top (open core, don't give away the special sauce) or deliver half assed products (package up the community leftovers and hope support contracts/services fill in the gaps).
That shouldn't matter if you're making a superior product.
I don't see it as a sound argument.
They would still be faced with knock-offs that either copy code or violate the license; Paint.net (https://en.wikipedia.org/wiki/Paint.net#History) is an example of this happening for an open source project.