What are my restrictions if I want to code node.js and use CoffeeScript? Can I do anything I'd be able to do in JS?
Yes, CoffeeScript simply compiles into pure JS, making it completely compatible with node.js.
To run CoffeeScripts on node, you can either:
coffee -c example.coffeeto compile, followed by
node example.jsto run the compiled JS.
Not only can you run CoffeeScript files directly in Node with
lib.coffee in a directory, you can write
require 'coffee-script' at the top.) So, you never have to do compilation explicitly under Node, unless you're packaging your project for deployment with a tool like npm.