Going to the IRS and saying, "This is how we plan to benefit humanity and because of that, we shouldn't have to pay income tax." and then coming back later and saying, "We decided to do the opposite of what we said." is likely to create some problems.

There is the tax issue, then there is being incorporated in Delaware issue.

He likely could bring some issue before the Delaware court as was done to him recently.

Can you imagine him having to go in front of the same judge again asking for corporate governance accountability? Zing!

Right, and when they decide to do the opposite they lose the tax benefit, I'm not really sure there's an argument that says they can't change their designation.

It matters though because they didn't change their designation before acting differently, which would make them liable. Not sure to whom they'd be liable though, other than the IRS.

OpenAI LP is the designation.

I don't understand what point your example or analogy is illustrating. Can you state the point you are making?

No one is alleging OpenAI committed tax fraud.

The point is possibly that there are rules that prevent organisations started as non-profit to transition to for-profit.

Note: I am just spitballing. I cannot speak definitely about the law or what the GP was saying.

True. Non profits exist, and they pay their leaders very well, and some that are probably corrupt provide very little benefit "for the greater good" or whatever the requirements are for non profit status.

Yes, the charter is legally binding as OpenAI's primary fiduciary obligation. It's akin to a normal corporation's duty to shareholders.

Such mission statements are generally modifiable as long as the new purpose is still charitable. It depends on the bylaws though.