There is one more way to customize Redmine—to modify Redmine itself, thus sharing your customization with other users. Any contribution is very important for free and open source projects, such as Redmine. An active and passionate community is what makes such projects good.
When most people hear about contribution to a free and open source project, they assume contribution in the form of some development, but in fact, there are many more areas where people can help. For example, this book helps Redmine by spreading information about it, teaching how to use it, and demonstrating its capabilities. Also, you have already helped Redmine by purchasing this book, not only because you can become a potential fan of this project, but also because Packt Publishing—the company that publishes this book—will pay a royalty to the Redmine team.
So let's discuss how else you can help Redmine:
Redmine.pm
. You can help even more if you know HTML/CSS and/or JavaScript because these technologies are intensively used by Redmine and may need improvements. If you are familiar with neither of the aforementioned technologies, you can still help by, for example, developing a REST API client library for Redmine using the technologies that you are familiar with.Here are some links regarding development for Redmine:
In a very similar way, you can help many free and open source plugins for Redmine.