Musk, a cofounder of OpenAI who is no longer involved in the company, sued OpenAI and its Chief Executive Officer Sam Altman late Thursday, alleging the company’s close relationship with Microsoft Corp. has undermined its original mission of creating open-source technology that wouldn’t be subject to corporate priorities.

OpenAI Chief Strategy Officer Jason Kwon pushed back at Musk’s suggestion that the startup is “a de facto subsidiary” of investor Microsoft and said the billionaire’s claims “may stem from Elon’s regrets about not being involved with the company today,” according to a copy of the memo obtained by Bloomberg News.

In a separate memo, also seen by Bloomberg, Altman called Musk a hero of his and said he misses the person he knew who competed with others by building better technology.

OpenAI declined to comment on the lawsuit or the two memos.

Musk is suing 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 OpenAI’s nonprofit parent organization as recently as 2019 and is seeking to force OpenAI to stop benefitting Microsoft and Altman personally.

Kwon pointed out in the memo that the company’s mission “is to ensure AGI benefits all humanity,” using a term that refers to theoretical software that can perform a wide range of tasks better than a human can. Kwon also said OpenAI is independent and competes directly with Microsoft.

Kwon also said he wanted to update employees on “inquiries from government agencies,” in an apparent reference to an investigation by the Securities and Exchange Commission that kicked off after the brief ousting of Altman by the company’s board late last year.

Kwon didn’t mention the agency by name, but said that “after the events of last November, they asked us for information and this matches what we’d expect given the circumstances.” Kwon said the company is cooperating with the government.