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.
For more information please see the following Australian Copyright Council Information sheet (page five onwards provides a table of Type of Material and the Rules that apply to it) :
It is the particular expression of an idea that is protected e.g. as a song, a novel, or a diagram.