I do wonder what value those companies who have >700 million users might get from this?

Pretty much all of the companies with >700 million users could easily reproduce this work in a matter of weeks if they wanted to - and they probably do want to, if only so they can tweak and improve the design before they build products on it.

Given that, it seems silly to lose the "open source" label just for a license clause that doesn't really have much impact.