Among developers, Meta's latest open-source large language model, the Llama 2, is the hottest thing around. Wall Street also seems to be waking up to the proposition, with the stock far outperforming AI rivals like Google and Microsoft. But calling Meta's AI system "open source" is only part of the story. And the same might also apply to buzzy startups like Mistral and open source’s loudest advocates like Elon Musk. This week on Tech Check, we break down the promise of open source AI vs the myth.