OAKLAND, Calif. — OpenAI’s president Greg Brockman got grilled by Elon Musk’s lawyer on Monday over embarrassing diary entries from nearly a decade ago in which he fantasized about becoming a billionaire — even as the then-nonprofit charity got millions in donations from Musk. “Financially what will take me to $1B?” Brockman wrote in the digital journal in 2017, referring to the idea of converting OpenAI to a for-profit entity. “We’ve been thinking that maybe we should just flip to a for profit,” Brockman allegedly wrote. “Making the money for us sounds great and all.” OpenAI President and co-founder Greg Brockman. Getty Images But Brockman — who, along with CEO Sam Altman, is being targeted by Musk for removal from OpenAI in a federal lawsuit in California that claims they violated the company’s charitable mission — also wrote down his reservations about the wildly lucrative game plan, court documents show.…