As you may know, C4 is a open-source project. This means that you can not only see the complete source code but also contribute your own features and improvements. In fact we encourage contributions. Contributions can in the form of code or documentation.
If you want to contribute code start by reading the Coding Standards which is a list of basic rules that help keeping the code consistent and therefore easy to follow. If you want to contribute documentation have a look at the Documenting Standards.
When you are ready to submit your contribution create a pull request. See GitHub's pull request help if you need help with this. The pull request (PR) will be reviewed by us and if approved will be merged to the master branch.
If you wave any comments or questions don't hesitate to ask.