This is just the content only, like images etc, no lua. Clients auto download this if the option is enabled in the config. This is so the clients don't download the whole addon + the server addon lua, but download the content and whats in the server addon lua folder. Aka it helps reduce the clients total download.

do you still need this now that the addon is in the workshop?

well thats confusing

Bad addon, crashed my game. I haven't downloaded it though