Lix is a fork of Nix (the program, "CppNix") and also an alternative community. They provide a few ways to install, like nixpkgs itself, but also a DetSys installer fork.

It's generally a response to corporate interests (including Anduril, who put Nix on autonomous weapons) and elbow-shoving so-called meritocracy (including a very infamous concern troll) becoming dominant inside the Nix community and Nix leadership, by people who didn't want to work from inside the system to reform, but also know they can't maintain all of Nixpkgs by themselves either (which already bled a bunch of maintainers).

Lix is a fork of nix-the-language and nix-the-program. In doing so, they forked the det-sys installer to install Lix instead of Nix.