It would be easy to dismiss Elon Musk’s lawsuit against OpenAI as a case of sour grapes.

Mr. Musk sued OpenAI this week, accusing the company of breaching the terms of its founding agreement and violating its founding principles. In his telling, OpenAI was established as a nonprofit that would build powerful A.I. systems for the good of humanity and give its research away freely to the public. But Mr. Musk argues that OpenAI broke that promise by starting a for-profit subsidiary that took on billions of dollars in investments from Microsoft.