Funnily enough, NixOS has had its initial release in the same year as Gobolinux, 2003.

I'm not sure how Gobolinux organizes files exactly, but with NixOS, the hash in /nix/store/<hash>-packagename is produced by combining every input that might influence the package. By input I mean for example:

- The source: git revision / source url / etc.

- All dependencies, which means if a dependency of a dependency of this package changes, it gets a new hash

- Build instructions, including build flags

This wouldn't be possible with a more conventional file structure.

It "does something similar" in the sense that it doesn't obey the FHS. NixOS is otherwise a pretty radically different approach AFAIK.