Well, the word 'open' is both incredibly generic, and very specifically what they're not. If there's confusion, it's pretty clear who started it.

I’m not a lawyer but from my understanding of trademarks, that doesn’t matter.

If it is confusing to consumers then it infringes. The genius is in “OpenAI” the actual company getting that name. And it’s just a name. They have no obligation to open their stuff.

If these guys said OpenSourceAI or OpenModels or something then it could work.

But IANAL. I just play one on the internet. :-)