Editors for EV Nova have been created that allow for the creation of third party universes, missions, ships, weapons, and planets. In fact, a whole new story line can be created for EV Nova to provide players with more to explore.
First go to EV Nova addons
and check out the utilities for making EVN plug-ins. Start with the EVN Bible for a guide to resource indexing.
Finally, the EV Developer's Corner is an excellent resource for plug-in developers. It is a web board where plug-in developers can post questions, hints and announcements. The Developer's Corner is even searchable, so you can check if your question has already been asked, and maybe even answered!
It is not a plug and play kind of thing, but it is much fun once you get the hang of it!