The attack surface for shellshock is insanely large, and it's crazy to leave bash unpatched even if one or two currently-known vectors happen to not currently be known to be exploitable. People will be finding ways to tickle it for years to come.
That's not applicable here. Even NetworkManager on Linux isn't susceptible to this hack. dhclient and dnsmasq can apparently be shocked on unpatched Linux, though.
2) People do use Macs as servers. It's unwise, clearly, but it is done. https://www.apple.com/osx/server/
3) OSX server is setup for CGI by default, all you have to do is throw some scripts in the right directory.