This plugin should work on all spigot versions from 1.8 and up. If it doesn't work on your version, just let me know and I'll make a build for your version.
When there is a staff member online
When there is not a staff member online
/who - Displays the list message. Aliases are /list, /online, and /staff.
betterlist.who - Use the command
betterlist.staff - Appear as a staff member.