The CM status is based on the code from
https://github.com/VoiDeD/steamstatus, the online users count comes from the "player" count for app 753, the GC stats are from maintaining a connection to each one (the actual information is game-specific, there is no standard), and the api/community/store stats are from just polling the sites. All of this can be done with SteamKit / C# (which is nothing to do with SteamWorks).