Prism is open-source. There's virtually no risk.

Regarding if your laptop is under attack, just check your list of processes and see if you find any out of the ordinary processes running. Remove TLauncher before doing this experiment. AFAIK, you're probably fine since malware on Linux is very very rare but better be safe than sorry.

It's always interesting how you can just be going on living your life and then someone tells you that there's this very popular fork of software you use that's been around long enough for you to wonder how and why it you're just finding out about it.

Its happened to me a lot.

MulticMC isn't abandoned, though it doesn't look like they're doing lots of significant updates these days.