When you mention "ground" in this context, I assume you are talking about "safety ground" on the mains AC. That is, the green wire on the 3-prong main AC cord.
Your Acopian supply is low power and encapulated, so I am guessing that is passes the 2-prong safety limits for UL. In fact, Acopian says that all models are UL Recognized. I don't know difference between UL Recognized and UL Listed. Perhaps there is a distinction between end-user devices (UL Listed wall-wart) and a supply to be installed into another product.
Per Bill Whitlock, the safety limits for 2-prong UL "listed" equipment are as follows:
- 0.75mA limit for leakage current (power line to chassis)
- Insulation creepage distances must be large
- Thermally protected
- Remain safe in spite of component failure, overload, and mechanical abuse
It appears that you could use a two-prong plug with this supply. With a three-prong plug, I would just connect the safety ground to the chassis of whatever device you are installing this supply into. I don't think you have to connect the safety ground to the supply since it is encapsulated.
I am not an electrical engineer or electrician, just a hobbyist. Your best option would be contact Acopian.