Which plugin should I use?
The BuycraftX plugin has 3 different versions for different platforms Bukkit/Spigot, Sponge and BungeeCord.
The most popular plugin is Bukkit and Spigot plugin which is designed to support Bukkit/Spigot v1.7.10 and above. BuycraftX is only tested with the latest versions of both Spigot and the Paper fork though so be aware of this when reporting any bugs. This is the fully-featured plugin, featuring not just command execution but also a GUI for browsing and purchasing packages, support for displaying recent purchases on in-game signs, and the ability to create direct purchase signs in-game.
The Sponge modding platform is a mix of client and server side modding and is supported by the BuycraftX Sponge plugin. It aims to track the latest version of SpongeAPI (as of 26 Sep 2016, it supports SpongeAPI 4.x). This plugin features command execution, support for displaying recent purchases on in-game signs, and browsing packages with an in-game display.
This plugin is for BungeeCord, the proxy solution for Minecraft offered by SpigotMC. BuycraftX works on the latest builds of BungeeCord and is a full port of BuycraftX for executing BungeeCord commands and BungeeCord plugin commands on BungeeCord proxies.
This plugin is for use with the Pocket Edition software called Nukkit. This plugin supports most of the normal features of the Bukkit plugin but will need to be used in conjunction with an offline webstore to support PE usernames.
This plugin is based in PHP and will support Pocket Mine servers though some forks of the original Pocket Mine have not been tested yet. You will also need to make sure that you are using this in conjunction with an offline webstore to support Pocket Edition usernames.