Event Organiser provides both a sophisticated API and a growing number of actions and filters that can help you achieve anything from a minor tweak to how it behaves to building an add-on – or just implementing a desired feature (such as front-end event posting).
If you have any questions feel free to head over to the forums.
Building an add-on.
If you’re thinking of building an add-on, I’d love to hear from you. If you’re thinking of distributing the add-on (for free or otherwise) it may be possible to arrange hosting or advertising from this site.