However, this is the copyright statement:
All products available via the anonymous FTP service are subject to the default terms of the Bureau's copyright notice: you may download, use and copy that material for personal use, or use within your organisation but you may not supply that material to any other person or use it for any commercial purpose. Users intending to publish Bureau data should do so as Registered Users.
I would say using the data on Windy would classify as "publishing". Here's where the fees to become a registered user are: http://www.bom.gov.au/other/charges.shtml
Here's a link to some sample data from the different radar packages (just match up the IDR number from the fees page: ftp://ftp.bom.gov.au/anon/sample/catalogue/Radar/
I'm not sure how much coverage of the country that is but there is also other options on that fees page.
Volumetric radar user manual:
Looks like the registered user costs are:
Service establishment: $1,025 (one-time)
FTP Access: $985 (per year)
1x radar package: $1,690.00 (per year)
+$345 if you were to change your service.
I'd be so excited to see weather radar on windy! I hope the people at the BOM are watching this thread. :D