alt Hacker News> You just need a sufficiently self-interested actor that sees open ecosystems as a necessary part of reducing their own risk profile, relative to the alternative of complete reliance of a third-party business that can take an exorbitant cut and/or Sherlock them at any time.
This would be an argument for an organisation developing its own model; but not per se for releasing the weights openly.
The possible explanations (I'm aware of, which overlap somewhat) for spending large amounts of money on models then releasing them for free (i.e. the current Chinese approach) are soft power, marketing for a future paid model business (i.e. competing with the US models for customers and mindshare during the time you can't compete directly at the bleeding edge), and/or a geopolitical move to diminish the value of the US's frontier model companies.
I acutally see the reduced burden that comes with actually sharing resources.
To extend the previous analogy: Valve didn't make desktop Linux viable on their own. A lot of it is owed to another self-interested actor -- Google -- through the reduced need for dedicated desktop apps (largely pushed by Chrome), and various enhancements to wireless and power management that were necessary to make it a viable mobile platform (directly benefiting Android/ChromeOS, but then spreading out to laptops and mobile devices in general, including handhelds like the Steam Deck).
You can see it on a smaller scale in ecosystems like Android -- where handset makers regularly contribute features from their UI skins upstream, so that they no longer need to spend engineering resources maintaining distinct versions of theming engines/notification badges/multiwindow/various other stuff.
On a related note this is an argument for open source models, not just open weights. I think a lot of the diminishing returns relate to the opaque nature of most models.