This is a discussion topic for the Ore project, DragonTranslations. View the full project on Ore for downloads and more information.
This is a resource to allow developers to easily add translations with little work on their end. I am aware that there's a pull request to add translation support into sponge itself via #1224 of the Sponge Api but I don't know when that will get completed/merged. I made this to use in the meantime while we wait for it.
For developers wanting to use this in their plugin, see the docs under developer use.
As a server owner using plugins supporting this, all you have to do is download it and install it onto your server like a regular plugin.