Ground Control Software (GCS) is a general term for software that runs on a PC, tablet, etc. that you use to communicate with the drone, create mission plans, and change autopilot settings. There are multiple GCSes out there, the most popular for ArduPilot are Mission Planner and QGroundControl. I think the HereLink comes with QGC installed, but I haven’t used it myself. I think you can update QGC from inside the app itself.
ArduPilot is the autopilot software that runs on flight controller hardware. “ArduPilot” is an umbrella that includes related autopilots for different vehicle types, such as ArduRover, ArduPlane, and ArduCopter. If your drone is a multirotor, then it’s running Copter. Instructions to update ArduPilot are here. Note that these instructions are for Mission Planner specifically, but QGC has a similar workflow and I’m sure there are instructions online for updating ArduPilot with QGC.
The service bulletins are released when an issue with the current software/hardware is found. These issues are usually fixed very quickly, so if your ArduPilot is up to date, then in general you won’t need to worry about old bulletins. I think the only ones that apply to current versions boil down to:
- Make sure you have a GPS lock when you do a compass calibration, and
- Don’t try to power peripheral devices off of the RC IN port (except a RC receiver).