communication.js

var PUBNUB = require("pubnub-browserify")
var config = require("./config")
var duplex = require("pubnub-stream/duplex")

module.exports = communication

function communication(doc, channel) {
    var client = PUBNUB.init({
        subscribe_key: config.subscribe_key
        , publish_key: config.publish_key
    })

    var stream = duplex(client, channel)

    stream.pipe(doc.createStream()).pipe(stream)
}

dead-simple.js

var crdt = require("crdt")

var communication = require("./communication")

var doc = new crdt.Doc()

communication(doc, "my room")

// And now it's synced to that room.