Could be a fight against Llama, which excludes MS and Google in its open license (though I think has done separate pay deals with one or both of them). Meta are notably absent from this announcement.
I was at the keynote, Llama was featured in the Copilot models section and called out specifically, as was Mistral.
I assume they just aren't at the point where they have the ability or want to host the compute to offer up Llama as an option as opposed to OpenAI, Anthropic and Google who are all offering the model as a service.
Ah ok, I thought the deal was giving them access to Github data too without the anti scraping stuff. And had this article in mind: https://archive.ph/FvI9G
