I think groups are actually called servers. If that's the case, a server can be created to run on its own (like any old server), and anyone can join it who has an access link (which the creator can give out).
Yes that, setting up a decent server securing it from "griefing" first. A also figured out the issue with old packs, 1.13 introduced a overhaul to resource pack formatting, so I am an hunting for some sort of automated tool to covert a old pack to new format for painterly fans to use before they apply the continuation patch.
Like any typical server that doesn't have proper safety protocols applied, a few examples: it could be flooded/overwhelmed if not secured, have people enter and make unwanted changes if proper permissions aren't set, or, most common I've seen, someone could abuse text chat (spam) or voice chat (constant interference).
The clock and compass in the current patch are incorrect and unnecessary. The clock and compass are actually correctly formatted in the definitive 1.10 painterly pack, for now you could delete all references to the clock and compass in this patch, till we release a fixed 1.14+ patch.
I think it would be best to make the next invite to the discord server (if and when you're making one) a permanent one, you can do that by clicking on the small text that says "Edit invite link." at the bottom of the invite window and then selecting "Never" in the "Expire after" field.
There hasn't been very much progress. Last updates were months ago but nothing complete. The Aquatic, Village and Pillage, and Nether updates are just so big and we don't have very many team members (most of which have gone inactive). I know I don't have the time or skills to make textures. The most I ever did was repurposed old textures.
Definitely join if you'd wish to help. We have a spreadsheet showing everything that we need to make. I may not have time to really help all that much but I still have all of my old resources. Maybe if I have some spare time I'll split the particles into their separate images.