Update: The HTML equivalent of the PDF is available at http://www.abs.gov.au/ausstats/abs@.nsf/Latestproducts/2901.0Main%20Features12011. Unlike the PDF, the HTML version is licensed under the Creative Commons Attribution 2.5 Australia license (and confirmed via email). I prefer the HTML version, I just hadn't noticed it earlier. Thanks to the Client Support Officer from the ABS who got back to me with this information.
Just a day after I posted my ASGS to PostgreSQL loader and plans to integrate with the ABS data, I've already hit resistance.
Once piece of documentation the ABS released for the 2011 Census data at http://www.abs.gov.au/ausstats/abs@.nsf/Lookup/2901.0Main%20Features802011/$FILE/2011%20Census%20Dictionary%2027102011.pdf (ABS Catalogue No. 2901.0) contains the full copyright notice without any reference to it being licensed under a free and open license such as the Creative Commons Attribution license. This notice is an "unless otherwise noted exception" to the CC license on the ABS website.
I made an enquiry to the ABS about this and was told "Written permission is required from the ABS if you wish reproduce this publication or extracts from it."
I'm disappointed that the ABS refuse to release their documentation for the 2011 Census data under a free license such as a Creative Commons license. It doesn't really make sense to me why they would release the data under an open license, but not release the documentation under the same or equivalent license. This only hinders the availability of the documentation and would lead to data consumers needing to make guesses or oversights about data and as such would be more likely to misinterpret it.