They're not that dumb, to just pull it completely. That would obviously result in a successful fork.

Companies usually start with e.g. the BUSL, so source-available but proprietary restrictions.
For TypeScript/Microsoft, I could imagine some variation of their EEE playbook.

But really, the whole point of avoiding Microsoft et al, is that I don't want to think about, how they could fuck this whole thing up. They've proven quite creative in this regard for as long as they've existed.