Mmmm, no. Nix is not a SaaS that builds your snapshots that you have to pay for (or that "they need to monotize", what's wrong with people?), it's a whole ecosystem ranging from a full OS (NixOS) down to a package manager (Nix Package Manager) and programming language (just "Nix).

Not sure what needs clarification here, it's pretty up-front about it's mission and features already.

> Your snapshots and abilities to rollback etc are likely to be dependent on their storage servers

Not sure where you get this from. Snapshots are stored locally unless you specify otherwise, and then you'll get to chose whatever storage servers you want to use. Absolutely no "hidden" costs with Nix as it's a MIT licensed project and I don't think they even offer any "value-added" services nor paid customer support.

Edit: reading the issue you just created (https://github.com/nix-community/wiki/issues/34), I'm even more confused. "Given the need to monetise" is coming from where? Nowhere do they say that they have to monotize but don't know how/where, so where do you get this from? Not everything is about money.