Only in the Land of the free
Unfortunately us Brits won't be able to join in with our special friends. I think we will fall afoul of the Computer Misuse Act off of 1990. I wonder if the US has anything similar?
The basic idea as presented here second hand (probably third), is a fair one if you are patriotically motivated, provided you want to assist "DARPA's mission is to create strategic surprise" whatever that means.
Mind you, given the sheer number of router manufacturers who have recently 'fessed up to hard coded credentials (Cisco, Juniper, D-Link, Fortinet - non exhaustive list) that mysteriously wormed into their firmwares why not? There are clearly a lot of bad actors out there.