This is not broken. When you require this module, it requires index.js from the root which requires coffee-script and then requires the coffee script files in /lib. This is transparent to the consumer; meaning, you do not need to require coffee-script yourself as a dependency.
To test this you could have just looked at the example code in the README and put it verbatim into your project. Notice it is not written in coffee script and doesn't require your code to install coffee-script.