Why use AMQP/ZeroMQ/RabbitMQ

Can I have each consumer receive the same messages? Ie, both consumers get message 1, 2, 3, 4, 5, 6? What is this called in AMQP/RabbitMQ speak? How is it normally configured?

No, not if the consumers are on the same queue. From RabbitMQ's AMQP Concepts guide:

it is important to understand that, in AMQP 0-9-1, messages are load balanced between consumers.

This seems to imply that round-robin behavior within a queue is a given, and not configurable. Ie, separate queues are required in order to have the same message ID be handled by multiple consumers.

Is this commonly done? Should I just have the exchange route the message into two separate queues, with a single consumer, instead?

No it's not, single queue/multiple consumers with each each consumer handling the same message ID isn't possible. Having the exchange route the message onto into two separate queues is indeed better.

As I don't require too complex routing, a fanout exchange will handle this nicely. I didn't focus too much on Exchanges earlier as node-amqp has the concept of a 'default exchange' allowing you to publish messages to a connection directly, however most AMQP messages are published to a specific exchange.

Here's my fanout exchange, both sending and receiving:

var amqp = require('amqp');
var connection = amqp.createConnection({ host: "localhost", port: 5672 });
var count = 1;

connection.on('ready', function () {
  connection.exchange("my_exchange", options={type:'fanout'}, function(exchange) {   

    var sendMessage = function(exchange, payload) {
      console.log('about to publish')
      var encoded_payload = JSON.stringify(payload);
      exchange.publish('', encoded_payload, {})
    }

    // Recieve messages
    connection.queue("my_queue_name", function(queue){
      console.log('Created queue')
      queue.bind(exchange, ''); 
      queue.subscribe(function (message) {
        console.log('subscribed to queue')
        var encoded_payload = unescape(message.data)
        var payload = JSON.parse(encoded_payload)
        console.log('Recieved a message:')
        console.log(payload)
      })
    })

    setInterval( function() {    
      var test_message = 'TEST '+count
      sendMessage(exchange, test_message)  
      count += 1;
    }, 2000) 
 })
})

Your question is a bit messy but Let's see its bits one by one.

General concept:

The Java Message Service (JMS) API is a Java Message Oriented Middleware (MOM) API for sending messages between two or more clients. JMS is a part of the Java Platform, Enterprise Edition, and is defined by a specification developed under the Java Community Process as JSR 914. It is a messaging standard that allows application components based on the Java Enterprise Edition (Java EE) to create, send, receive, and read messages. It allows the communication between different components of a distributed application to be loosely coupled, reliable, and asynchronous.

Now (from Wikipedia):

The Advanced Message Queuing Protocol (AMQP) is an open standard application layer protocol for message-oriented middleware. The defining features of AMQP are message orientation, queuing, routing (including point-to-point and publish-and-subscribe), reliability and security.

And the most important thing (again from Wikipedia):

Unlike JMS, which merely defines an API, AMQP is a wire-level protocol. A wire-level protocol is a description of the format of the data that is sent across the network as a stream of octets. Consequently any tool that can create and interpret messages that conform to this data format can interoperate with any other compliant tool irrespective of implementation language

Some important things you should know:

1. Keep in mind that AMQP is a messaging technology that do not implement the JMS API.
2. JMS is API and AMQP is a protocol.So it doesn't make sense to say that what is default protocol of JMS, of course client applications use HTTP/S as the connection protocol when invoking a WebLogic Web Service.
3. JMS is only a API spec. It doesn't use any protocol. A JMS provider (like ActiveMQ) could be using any underlying protocol to realize the JMS API. For ex: Apache ActiveMQ can use any of the following protocols: AMQP, MQTT, OpenWire, REST(HTTP), RSS and Atom, Stomp, WSIF, WS Notification, XMPP. I suggest you read Using JMS Transport as the Connection Protocol.

Good Luck :)