this game is a mod, thus the devs aren't making any money from it, thus they cant be sued for using someone elses IP for making money
it would be like sueing you for drawing a picture of a mech and giving it to your friend, you made something for free and are giving it away for free
Actually they can, but they don't feel the need to since it's an independed non-commercial usage of the IP which we've liscensed from MS.
Square Enix has shut down numerious other fan projects relating to their IP's, despite them being developed as free releases. It just depends on how much of a "financial threat" a project is that a company views in order for them to actually want to act on it.
Not saying anyone gives two cents about Robotech anymore. I think the only reason why Harmony Gold is doing the stuff with Smith and Tinker is because they know that S&T/MS have money - money that they could leech from by trying to do a liscense agreement/sueing. We on the other hand have no financial background, so them sueing/C&D'ing us makes no sense on their part as they would gain nothing from it.