Features Sulfur lets you easily create queues between different worlds without having to rely on Bungee or other proxies. Initially this plugin was created as a way to try and monetize a minecraft server without breaking minecraft's eula, but it's become a very customizable plugin.
Installation You just have to put the jar file inside the plugins folder and then restart your server. The queues are contained in the queues.yml file, and you are free to modify this file to change queues information while not in-game. However, there currently isn't any config.yml file to change the messages used by the plugin, it is a planned feature and should be introduced in a future update.
Commands/Permissions There are currently four commands used to manage or interact with the queues. Two of these are considered admin commands (/sulfur createqueue and /sulfur removequeue), and they can only be used by players with the "sulfur.admin" permission. The other two commands (/sulfur joinqueue and /sulfur leavequeue) are supposed to be used by players with the "sulfur.user" permission, which is assigned by default.
Source You can check Sulfur's source code on our github page.