[remram]

In the USA, being sued is 99% of the punishment, losing the suit does not really matter. Especially when faced with a big corp like this.

You should think about what might get you in legal trouble, whether you might prevail is not relevant to your bottom line unless you are a Fortune 500 yourself.

[lolinder]

Unfortunately, by that logic you could conclude that competing with Microsoft at all would be out of question because in theory they could sue you into oblivion with a completely arbitrary lawsuit.

The real world isn't quite that bad, so OP is correct to observe that Microsoft does not in fact have a trademark on Copilot, they have a pending trademark on Microsoft Copilot and GitHub Copilot. Given that their own trademarks (owned by different subsidiaries) include a second word to qualify them and would pose a substantial risk of confusion with each other if Copilot alone were treated as the mark, I think it's reasonable to argue that Microsoft couldn't claim a trademark on Copilot, unqualified, and is unlikely to even try to assert it.

[remram]

> you could conclude that competing with Microsoft at all would be out of question because in theory they could sue you into oblivion

That is my conclusion yes.