It's open source and only 200 lines of code - https://github.com/immers-space/guppe
I think the reason why they didn't relaunch it under another name is because the developer didn't want to. And they didn't want to because unmoderated groups are a bad idea and making them moderated would need more than 200 lines of code.
Once I got a.gup.pe integration working with PieFed I was very disappointed to find that 95% of the groups are either abandoned, full of spam or full of really really low quality content. The only good one was the photography one which I converted to a piefed community - https://piefed.social/c/photography