Hi @Truman_Chen-
Others have chimed in here and I don’t have much to add, but I’ll add anyway 
Grasshopper is only available in the RhinoWIP. It only runs if you have purchased Rhino 5 for Mac or if you are in your 90-day evaluation window (Rhino 5 for Mac and the RhinoWIP use the same license).
We renamed the command back to Grasshopper.
The ExplicitHistory command still runs Grasshopper, but it does not autocomplete.
You can read more about this and other Grasshopper for Mac issues in the Grasshopper for Mac category.
I hope that helps clarify,
-Dan