The main idea is to make an official NPM mirror as detailed here: https://github.com/npm/npm-registry-couchapp
Unfortunately the above instructions appear to be flawed and didn't working for me. Thankfully someone has taken the time to create an updated set of installation instructions: https://github.com/rvagg/npmjs.org/tree/new-install-docs
Only one problem remains with the above instructions and that is the credentials for the copy script. In copy.sh you need to fix the credentials for curl. Change this (line 46):