The author might not be malicious, but from going through some of the audio packs, they're really not quality-checking PRs. For instance, sc_medic/sounds/WhereDoesItHurt.mp3 sounds like two-and-a-half sounds stuck together ("Critical? You Rang? Please state the nat--", it cuts off right there, and doesn't include the phrase "Where does it hurt?").

I wouldn't use this repo outside of some kind of sandbox.

I don't think using something fun as an attack vector is anything new at all. It's an easy way to have someone let their guard down because you want to play around and aren't thinking how something silly could actually be out to get you.