I'm sorry but I got stuck on the first sentence "Ted Unangst published dude, where are your syscalls? on flak yesterday" and as a long time fediverse operator I

I'm sorry but I got stuck on the first sentence "Ted Unangst published dude, where are your syscalls? on flak yesterday" and as a long time fediverse operator I got insanely curious about "flak". So I ended up on the flak tag of this blog[1], but I still can't figure out what it is. I can find no links to any source code, or any service description. Even though the blogger mentions flak being their "signature service". I'm guessing it's a blogging platform, with ActivityPub support, but I can't find any info about how it's used. 1. https://flak.tedunangst.com/t/flak https://flak.tedunangst.com/t/flak