Achive & earn

Lowkey, I download the add on and put it on my realm, but then the books looked different from when I tested it on a separate world and when I used the guide book it was crediting different people and said the add on with a different name. I checked the marketplace because the different book textures felt like cheesy add on ones, and lo and behold when I searched the different name, it was there. Why is the realm replacing the add on with the marketplace one and why are there even two. Who stole who