That is correct, DIY Edition comes without an OS installed or an OS license (though you can add a Windows license).
We’ve made the setup process for the DIY Edition really straightforward, and we think kind of fun too: https://guides.frame.work/Guide/Framework+Laptop+DIY+Edition...
Yeah, but I’d rather not pay for that Windows license.
Edit: Oh, I see that you have to DIY the entire laptop in order to NOT select a Windows OS.