I dont see a problem with the entirety of the plugin being private, but the core concept and general rules/configuration of the gamemode should be freely available or well documented atleast.
If they want this gamemode to succeed as a competitive gamemode someone needs to set the standards, so theres as little difference from server to server with all the aspects that can change times on maps and such, if they don't someone will probably set the standard at some point and then HoC is going to be the ones who are not following it, that all depends if the gamemode is not dead by that time.