[disclosure: I'm one of the guys developing it]
* GoboLinux isolates software in OSX .app-like directories
* GoboLinux is much older
* GoboLinux has a better logo
Both projects were started around the same time (2002). I _think_ we might have been ahead for a few months, but my memory may be failing me. I was shown Nix not long after Gobo was in the news for the first time (ah, the days of Slashdot and Kuro5hin... ;) )
I haven't looked closely at Nix for a long time, so things might have changed, but the main difference between Gobo and Nix, I think, is the degree of access you have to tweak the system by yourself.
Gobo keeps things directly user-tweakable (you can install your own programs with `./configure --prefix=/...; make; make install` if you want and Gobo will see it as a first-class citizen of the system), while Nix manages your filesystem tree on its own (it uses directories with hashes in its names, etc) so the user should only interact with packages via Nix's own tools. Of course, this is important so that Nix keeps its functional guarantees.
The goal in Gobo, on the other hand, is to give user full control (if you mess it up, it's your fault — but with a more organized filesystem, it's harder to mess it up).
And thanks for the compliment on the logo. :)
http://sandervanderburg.blogspot.com.br/2011/12/evaluation-a...
Maybe some of the experts here on HN can comment on how accurate and up to date it is?
As far as Gobo is concerned, the outdated parts is that the /System/Links/{Executables,Libraries,...} has been replaced by /System/Index/{bin,lib,...} which makes it easier to build packages (less compatibility issues to deal with, since /usr is a symlink to /System/Index). So it's easier for a user to compile their own stuff and get it working.
And of course, the comment at the end about the project inactivity no longer applies: Gobo is alive and well. :)