The original headline "Elon Musk used to say he put $100M in OpenAI, but now it's $50M: Here are the receipts" should be used here, this seems editorialize.
I mean plenty of companies have company cars so at face value I suspect a charity having a company car is not fraud.
But also if say a charity wanted to feed orphans and you donated 100M to them in 2015 and then in 2018 they announced they were going to start funding farms instead with the idea that more food produced meant more food would get to orphans I don't think you could sue them for your 100M back. Charities are going to evolve over time and I don't think the OpenAI evolution has reach the level of fraud.
Which part is the "theft". They existed to make AI and behold, they did AI.
You can argue they didn't open-source it, as their name suggests, but they also were denied a billion of funding that Musk kept promising until they were literally out of money.
What they did was a matter of survival. Of course they're not blameless in their actions now. They're clearly building a very powerful business. But they were put in this position. It was either this, or OpenAI wouldn't exist.