It seems to work in CS4 too!
Opening the test file gave me some errors:
"This document contains unknown data which will be discarded to keep layers editable. […]"
and
"Some groups were found corrupted and repaired."
Running the script on that file gave me a Spriter file and accompanying png files, so that it looks the same as the psd file when it's loaded into Spriter. But I got no bones.
The problems with it are obviously the 5 nested groups limit you mentioned. Instead of a "root" group, I get an empty and hidden "root" layer. If I remove enough parts so that it fits in five nested groups, put the bones in a root group, and hide the bone layers, I do get bones. Odd looking (all horizontal - but I guess that's how it should be, as the bones in your sample spriter file looks the same), but functional bones.
So thanks! It is indeed working in CS4 too. The bone creation is less useful due to Photoshop's group limitation, but even without that, I'm sure that it'll prove useful!