I've noticed that when I work with arcpy and multiprocessing together, that it can cause a runtime error: "Runtime Error: The Product License has not been initialized". From what I can tell, this is happening because every pool that is created is trying to import arcpy and is pulling a license from the licensing server and at some point the server runs out of licenses. If I keep the number of pools low, then this error doesn't occur.
On that note though, I don't understand why I would be limited to one instance of arcpy on my computer since I do have a license that I am using. Is there a way to tell arcpy to use my current license without pulling a new license every time a script is run?