Musk filed the lawsuit last week against OpenAI, CEO Sam Altman and president Greg Brockman, alleging the startup had strayed from its mission to build responsible AI and that it had become beholden to Microsoft Corp., its largest investor. In the post, OpenAI said that Musk was lashing out after trying and failing to make the company part of Tesla Inc.

“We’re sad that it’s come to this with someone whom we’ve deeply admired — someone who inspired us to aim higher, then told us we would fail, started a competitor, and then sued us when we started making meaningful progress towards OpenAI’s mission without him,” the company said in the post, which was co-authored by several of OpenAI’s co-founders, including Altman, Brockman and Ilya Sutskever.

The post also reproduced emails Musk had sent to people at the company, demonstrating that the billionaire had endorsed OpenAI’s fundraising efforts. “This needs billions per year immediately or forget it,” Musk wrote in one email, according to OpenAI. 

OpenAI, as a non-profit, raised less than $45-million from Musk and more than $90-million from other donors, according to the blog post. Musk pushed the company to be far more ambitious in its fundraising, the emails show.

At the outset, Altman and Brockman planned to raise $100-million, OpenAI said in the post. “We need to go with a much bigger number than $100M to avoid sounding hopeless relative to what Google or Facebook are spending,” Musk wrote in an email cited by the startup. “I think we should say that we are starting with a $1-billion funding commitment… I will cover whatever anyone else doesn’t provide.”

Musk alleges in his suit that the startup’s close relationship with Microsoft has undermined its original mission of creating open-source technology free from undue corporate influence. “To this day, OpenAI Inc.’s website continues to profess that its charter is to ensure that AGI ‘benefits all of humanity’,” the lawsuit said, referring to artificial general intelligence, a powerful type of AI that doesn’t yet exist. “In reality, however, OpenAI Inc. has been transformed into a closed-source de facto subsidiary of the largest technology company in the world: Microsoft.”

Musk had also signed off on the idea that OpenAI wouldn’t build open-source software for artificial general intelligence, and that it would not always share the science behind its technological advances, according to OpenAI. “As we get closer to building AI, it will make sense to start being less open,” Sutskever wrote in a 2016 email cited by the startup. “The Open in OpenAI means that everyone should benefit from the fruits of AI after it’s built, but it’s totally OK to not share the science,” the e-mail reads. In his response, Musk replied, “Yup.”

In the blog post, the OpenAI co-founders said that Musk hadn’t always been opposed to corporate influence at OpenAI. They said that Musk had written in an e-mail: “Tesla is the only path that could even hope to hold a candle to Google. Even then, the probability of being a counterweight to Google is small. It just isn’t zero.” 

Musk is suing the startup for breach of contract, breach of fiduciary duty and claims of unfair business practices, among other grievances. He is bringing the suit in the capacity of a donor to the nonprofit parent organisation as recently as 2019, and is seeking to force San Francisco-based OpenAI to stop benefitting Microsoft and Altman personally.

Co-authoring the blog post marks a return to public view for Sutskever, the company’s chief scientist and a former OpenAI board member, who had voted to oust Altman in November but later recanted his decision to help fire him.