That's quite the headline. Is it justified? From the article:

the nonprofit will now only hold equity OpenAI claims is valued at approximately $130 billion [...] as opposed to its previous status of holding the bulk of the profit interests in a company valued at (when you include the nonprofit interests) well over $500 billion

...

Even if we thought the new control rights were as strong as the old, we would still be looking at a theft in excess of $250 billion, and a plausible case can be made for over $500 billion. I leave the full calculation to others.

This is all speculative value - what stockholders think it's worth, and they could be wrong. But still.

On the other hand:

the nonprofit, after the theft and excluding control rights, will have an on-paper valuation only slightly lower than the on-paper value of all of Anthropic.

...

If OpenAI can successfully go public at a $1 trillion valuation, then depending on how much of that are new shares they will be selling the nonprofit could be worth up to $260 billion.

For comparison, the Gates Foundation had about $77 billion at the beginning of the year.