Current documentation on moving/copying an AUSkey between Macs is scarce, below are recent steps taken for a successful AUSkey migration.
On the new Mac download and install the AUSkey Chrome & Firefox plugin from the Australian Business Register.
On both Macs, open Finder > click Go in top menu bar > hold down an option key and select Library from the menu.
Copy the following two directories from the old Mac to the same place on the new Mac:
~/Library/AUSkey
~/Library/Application Support/AUSkey
Note: AUSkey no longer requires Java to be installed.