Native APIs are exposed as JS modules. And XHR, for example, is polyfilled in terms of whatever native capability exposed. You can totally use npm modules, provided any module that it uses is polyfilled.
My bet is that they are working with thrift for their transport layer. We're moving the same direction. I should be landing a bunch of diffs over the next week to the JS thrift libraries to support XHR and websockets in the nodejs thrift library (for use with browserify).
