My take is it’s cringe.
Re Nix 3.0, to the extent that they’re using the word Nix in a way that would violate our hypothetical trademark policy, they should not do that.
Edit: On reflection, I would like to say something stronger. The branding ‘Determinate Nix 3.0’ in particular is very likely to cause confusion among people who might think that it is in fact the next version of Nix. Intentional or not, that’s bad for the community regardless of the presence of an enforced trademark policy. Pulling PR stunts with your version number is one thing, and calling your downstream project ‘Company Name Upstream’ is another, and each of those to me are like, eh, not great but whatever. The combination is worse because of the anticipated consequences for people who are not actively following the details of what’s going on. Please rethink one or both components of this, DetSys.