This is a custom deployd resource type allows you to write code that can be required by other resources.
In your app's root directory, type npm install dpd-codemodule --save into the command line or download the source. This should create a dpd-codemodule directory in your app's node_modules directory.
See Installing Modules for details.
You can write your reusable code inside the Index event. Follow nodejs module conventions by using exports.somename = ...;. See nodejs modules documentation for more details.
Later on in your event code, you can use:
var myCodeModule = requireModule('coderesourcename'); and you will have access to the code shared by the module.
This resource explicitly adds the requireModule(name) global function which acts as a helper function for finding the proper path of the module.
Alternatively, you can use something like require('../../resources/coderesourcename').