Why would every company do it though? They'll just all be using the same (Anthropic's) AI-enabled fork.

You think Anthropic wants to be the sole maintainer of thousands of forked OSS projects...? I seriously doubt that would happen, for legal, marketing, and logistical reasons alike.

Anthropic, probably not. I could totally see Altman or even Musk deciding to do that exact thing as a showcase of sorts.