I don't have a EdgeRouter myself, but if I got the Ubiquiti forum information right, it is possible to add code to the router. The only issue is if the router has a P2MP IPIP driver in its kernel, so that ampr-ripd could be used. If not, amprd which runs entirely in user space could be an option, assuming the router's kernel supports tun/tap interfaces.
This is a nice experimentation point :-)
Marius, YO2LOJ