There has been some work to get Carbide Motion to run in Linux, but I don’t think they’ve compiled it for an RPi.
Linux version: http://carbide3d.com/dl/CarbideMotion.tar.gz — a bit of discussion on it here: Carbide Motion Test/Beta and here: SO3: Will LinuxCNC work?
belike you’d be better served using some opensource comm / control app better suited to an RPi — we list some here: http://www.shapeoko.com/wiki/index.php/Communication_/_Control#Raspberry_Pi