OAKLAND, Calif. — One of the biggest trials in tech is underway, and it did not take long for the accusations to start flying. Tech mogul Elon Musk took the stand Tuesday in the first day of testimony for his lawsuit against OpenAI CEO Sam Altman, claiming Altman, his onetime associate, had betrayed the altruistic principles the AI company they co-founded was built on. Musk also took much of the credit for OpenAI's creation. “I came up with the idea, name, recruited the key people, provided the funding,” he said in court. “I could have started it as a for-profit, and I chose not to.” The outcome of the trial could determine the future of OpenAI, which was founded as a nonprofit operation in 2015.…