Hmm, I am not sure if they would have very sophisticated software on the lander, in the way your thinking. I don't think any processing is done on the lander itself. It might be just primarily used as a remote sensing telemetry system. I suppose the lander would have a lot of power management circuits, some control circuits, sensor-actuator circuits, and transmitter-receiver communication circuitry. There would probably be a RTOS for real-time measurement and actuator motion.

Still, I think someone with specific expertise might give a better answer.