Elon Musk said today its AI firm xAI will take immediate legal action against Apple for not putting either X or Grok in the Must Have section of the App Store despite X being the No. 1 news app in the world and Grok is the fifth most used app, according to charts. Apple is putting OpenAI first in the App Store, which is an unequivocal antitrust violation, according to Musk.