Spent convictions rules
I think Assange was convicted of hacking more than ten years ago now.
See http://www.afp.gov.au/what-we-do/police-checks/spent-convictions-scheme.aspx
"Spent Conviction Scheme
Convictions covered
The scheme applies to spent convictions where a waiting period has passed and the individual in question has not re-offended.
The following conditions apply to convictions for a Commonwealth, Territory, State or foreign offence:
* it has been 10 years from the date of the conviction (or 5 years for juvenile offenders)
* the individual was not sentenced to imprisonment for more than 30 months
* the individual has not re-offended during the 10 year (5 years for juvenile offenders) waiting period
* a statutory or regulatory exclusion does not apply
The scheme also covers convictions that have been set aside or pardoned under Part VIIC of the Crimes Act 1914. An individual whose conviction is protected does not have to disclose the conviction to any person, including a Commonwealth authority."