The eventual goal is to have configuration happen in the web interface.
The eventual goal is to support other solutions, such as multiple interfaces. For now, the only supported model is a computer with a single interface, and an alias created for the 2nd network. (Also known as one armed router, or router on a stick.)
.deb file is available for jsoncpp, I'd rather be using that than building 3rd-party libraries within Myra Canyon. Check when Ubuntu 15.04 or later comes out to see if a package is available for jsoncpp. IPv6 is not yet tested. Likely broken in many places. Leave it disabled until it is time.
ARP wont work. Iptables is just for IPv4 and IPv6. Instead, use ebtables for ARP. Though it looks like ebtables doesn't yet support the NFQUEUE jump target, so not much we can do.