He called OpenAI boss Sam Altman a "liar" - after Altman claimed Musk used his platform to "benefit himself and his own companies". The row is the latest flashpoint in what is an ongoing feud between the billionaires who co-founded OpenAI - but now fiercely compete after Musk left the firm. Apple announced a partnership with ChatGPT in June 2024 - but there is no suggestion Apple favours one app over the other, and several rival AI apps such as DeepSeek and Perplexity have topped the App Store charts since then. The BBC has approached Apple for comment. In a later post Musk took aim at Apple again, asking the firm why it would not promote X - or its AI app Grok - in the "Must Have" section of the App Store. "X is the #1 news app in the world and Grok is #5 among all apps," he said in a post now pinned to his X profile. ChatGPT is currently the most downloaded free app in the UK, with Grok a close third. X does not make the top 40. This seemed to draw the attention of Altman, who linked to a report by tech newsletter Platformer which claimed Musk had made his own personal X posts more prominent in people's feeds. (BBC)