Edit: CORRECTION! This is a person that used to use the cznic nickname, maybe because they worked in CZNIC for a while, but now goes by "modernc"
Seems like they've been involved in transpiling C projects, like TCK, to Go.
Some context: https://news.ycombinator.com/item?id=33197603
==previous message before my edit==
Oh, seems like this is made by CZNIC, the org that admins .cz TLD.
They've also done the Omnia Turris routers, KNOT DNS server or BIRD routing daemon...