Orphan works are works where the copyright owner cannot be identified and/or located to ask permission to use the work.
Australia's national and state libraries have adopted a 'reasonable search' approach to determine whether or not a copyright owner can be identified and contacted. The reasonable search is explained in a National and State Libraries Australia position statement.
An orphan work's appearance on the State Library's catalogue and image viewer does not guarantee that it can be used for any other purpose besides research or study.
If you are considering other uses see the Australian Copyright Council's Orphan Works fact sheet. It includes the advice:
"If you want to use an item protected by copyright and you cannot identify an owner, you will need to make your own risk decision about whether or not you want to go ahead and use the material anyway…
If you do choose to go ahead and use orphaned material, we recommend you use a 'good faith notice' with the material. This is essentially a notice to indicate that you have tried to find the relevant owners and which invites any owners to come forward should they have a problem with what you are doing."
The State Library's good faith protocols include our Takedown Policy.