No.

The page you link has the foundation’s leadership structure. He’s a cochair on the board with 8 total people. The board is a degree removed from day to day operations of the foundation. He’d have to convince the board to then convince the executives.

That transaction would then show up in their financial statements, which are audited and publicly posted on that website. Meaning using the foundation’s money for something like a private jet would likely become public knowledge within a couple years and would do irreparable harm to the foundation’s reputation. Maybe they could hide it but good luck convincing everyone involved it’s worth the risk without a shitload of additional corruption.

I’d very much doubt he can just use it any way he pleases, or for personal use at all for that matter.

I don’t know about charity law in the US, but the point of a foundation, I think, is that you lose control of the money, and in return don’t have to pay tax on it anymore.

That’s not to say that shenanigans aren’t possible, or that he doesn’t still have a say, but I don’t think he could use it the way you’re describing.

can he spend that foundation money any way he wants

Yes and No. Yes, he can make the decisions. No, the purpose is somewhat limited.

But since he created this foundation and defined it’s purpose, it will always do what he wanted to do anyway.

instead of spending his personal money?

Above some certain level, your personal expenses simply don’t matter anymore. You can throw money around all day long, but you cannot become poor again.

Bill Gates hasn’t technically been the richest person in the world for a long time.

Even his own net worth is not money he can just spend. He doesn’t have 5 billion in his bank account. He owns assets in different levels of liquidity whose value fluctuates.

Think of it like he already spent that money. It belongs to the foundation now, not to him.

https://youtu.be/69AtkAHkKEc?si=zCei4ckJEQd13snJ

A good idea of how billionaires use charitable donations.