The old add-on has been removed (Purple Powers and Purple Remake)

So, the add-on you're seeing is probably actually an official one from the user Bacon Master, but published by the team. 

ADD-ON:

Purple RMK is a Minecraft addon about bosses and powers

As the addon is still under development, expect many changes

The addon also features a system of missions, parries, bosses, and powers, but it also has its own story that you, the player, will have to discover.