The case against ChatGPT maker OpenAI is "a textbook tale of altruism versus greed," the complaint filed in a federal court in California alleges.
"The perfidy and deceit are of Shakespearean proportions."
The filing of the complaint by the billionaire Tesla and SpaceX co-founder comes nearly two months after he abruptly withdrew a similar suit against OpenAI, Altman and Brockman.
Musk, who left the San Francisco-based OpenAI in 2018, accuses them in the latest complaint of fraud, conspiracy and false advertising.
He said he originally invested in OpenAI in 2015 with the understanding that it would be a non-profit, but Altman "manipulated and deceived" him, eventually joining forces with software giant Microsoft.
"Altman assured Musk that the non-profit structure guaranteed neutrality and a focus on safety and openness for the benefit of humanity, not shareholder value," the suit says. "But as it turns out, this was all hot-air philanthropy -- the hook for Altman's long con.
"The resulting OpenAI network, in which Altman and Microsoft hold significant interests, was recently valued at a staggering $100 billion," the suit says.
"As a result of their unlawful actions, Defendants have been unjustly enriched to the tune of billions of dollars in value, while Musk, who co-founded their de-facto for-profit start-up, has been conned along with the public."
OpenAI captured the public's imagination in late 2022 with the release of ChatGPT, which can generate poems and essays and even succeed in exams. The firm has also developed image and video generating tools that are seen as leaders in the field.
Microsoft, a major investor in OpenAI since 2019, poured billions more into the firm last year.
And the software giant stepped in when OpenAI's board fired CEO Altman in November, hiring him and offering to house any staff members who were unhappy with his ousting.
The OpenAI board reversed course as dissent soared in the company, reinstating Altman and replacing several board members.
Since leaving OpenAI, Musk has joined the chorus of critics warning that artificial intelligence could spell the end for humanity.
He launched his own AI firm, xAI, last year.
Musk is seeking a jury trial and unspecified damages.
