The script gets all of the publicly federated communities and "makes them known" to your local instance and then subscribes to them. "All" should be populated with activity from around the Lemmyverse.

Doesn't that significantly increase the load on your instance and, if many instances use it, all instances? This system isn't designed with the idea that each instance receives everything from every other instance.

It might be better to run this on a single dedicated site which people can come to to browse. If you could learn where each user had their account, you could send their upvotes, downvotes and comments to that instance.