From what I understand is that the crew were ordered to depart by Operations which I would expect would have been approved by senior management considering the financial implications for departing after curfew.
This has nothing to do with the pilot. He followed company command for an act that did not place him, his crew, the aircraft or the passengers in any danger.
It must be obvious that it was in the best interests of Jetstar to send the aircraft versus park it for the night and overnight all passengers (on both sides) plus handle the follow-on disruption this would have caused. With only a few aircraft in the network, any disruption to the 'highly untilised' 330 fleet would probably cost the organisation more then what the fine did...
Obviously this is not a common event - in 5 years of operation this is the only such breach of curfew. The airline made a decision which was in its best interests for the airline and its customers.