Contractual agreements can take the form of legal documents signed by both parties but may also include the shrink-wrapped, click-on and "read me file" licences, terms and conditions and subscription agreements associated with electronic products (e.g. electronic journals available via the Internet, textbooks on CD-ROM, multimedia kits, etc).
Most copyright owners of digital material provide their material under licences. This means that if you are using material in digital form, how you can use the material will be determined by the licence, rather than provisions in the Copyright Act 1968 (Cth). The licence may allow uses not allowed under the Copyright Act, and vice-versa.
Just because material is freely available, doesn’t make it free to use. Material on the Internet like music, videos and photographs may be protected by copyright and in many cases, permission to download material from a website is given on the site itself; but the fact that material is available to be viewed on a website, or is accessible using networks over the internet does not, by itself, mean that you can use it as you wish.
Copyright does not last forever, and once it has expired you can copy material without the copyright owner's permission. Precisely how long copyright lasts, however, depends on the type of material, so check first.