This is the Main Roads Western Australia Road Network (MRWA-514) dataset converted to OSM format.
The original dataset (https://catalogue.data.wa.gov.au/dataset/ntwk-iris-road-network) has been released under the Creative Commons CC BY 4.0 licence and requires the following notice to be included when you share the licenced material:-
The Commissioner of Main Roads is the creator and owner of the data and Licenced Material, which is accessed pursuant to a Creative Commons (Attribution) Licence, which has a disclaimer of warranties and limitation of liability.