Interesting. From what I can see, it just tricks any CommonJS style module into thinking that the module and exports variables are available; and that it's running in a node like environment. Things like accessing the file system and http wont' work, but that doesn't seem to be what it's meant for - it's more "write your client side js in a testable common js format, declare dependencies like backbone and underscore, and you'll get a neat little browser runnable package at the end".