Core is a open source plugin providing a good foundation for any server using Sponge (https://www.spongepowered.org/) It's commands are very extended so you are able to rollback your banlist, create private warps and invite players, add limitations for anything (ex: tempbanning).. and a lot more! Feedback is always appreciated and can be written down at Core's official thread at the sponge forums.
Core is licensed under the MIT license.
If you found a bug you can contact me at anytime on GitHub, SpongePowered or you can use the official thread and report your bug in the comment section. Don't forget to leave a link for your server log as the log is needed to identify the exact line where it's causing the error.
The wiki provides useful informations on installing & updating Core as well as its commands & permissions. Here's a quick navigation of the current pages: