Thanks for the response! I guess I was referring more to the extensibility of Moodle when it comes to extending or overwriting existing features with more functionality via custom development.
As you mentioned, it's open source, but I would want to avoid modifying the original source since that essentially forks the Moodle source and creates a situation where upgrading Moodle (as new updates come out) is very difficult (if not impossible). For example in Wordpress, you can extend Wordpress to do just about anything you want without having to edit WP source code. I'm hoping there's similar capabilities within Moodle?