How does GoboLinux distinguish between packages of the same version compiled under different environments, or compilers, flags etc.? In Nix such changes cause the resulting build to be prefixed in /nix/store with a different hash.
I'll venture a guess: It doesn't need to. All of the "first-class citizen" packages, which are visible to everyone, were built in the same environment, just like in other distros. Alternative versions should just be held separately.
... but come to think of it - that means that you can't just put your package in /programs/MyApp/12.3.4 - because if you switch your system to that version your dependencies may well break. Hmm.
