PufferPanel is an open source game server management panel designed for both small networks and game server providers. PufferPanel supports Minecraft, Spigot, Sponge, Source Dedicated Servers, BungeeCord, PocketMine and much more.
Crafty is a wrapper for a Minecraft server which runs in the background. It has tons of features, including a slick AdminLTE-based GUI, auto-backups and console commands.
Purpur is a Minecraft server fork of PaperMC that aims to provide high-performance Minecraft servers as a replacement for Paper and Tuinity.
Paper is a fork of the Spigot server implementation (which is itself a fork of CraftBukkit). Paper strives to bring improved performance, more features, and more APIs for developers to build awesome plugins with.
When exploring for plugins to add to your server, I recommend that you take a look around on Modrinth with the "Open Source" filter enabled. Modrinth is also a great place to look in for datapacks to add to your server's worlds and more.
WorldGuard is a powerful plugin with a large bag of tricks for server owners, server map makers, regular survival servers, and everyone in between!.
WorldEdit is an easy-to-use in-game Minecraft map editor. Through a combination of commands and "brushes," you can sculpt your world or simply perform numerous terraforming tasks.
