A good that is made available at zero price is not necessarily a free good. For example, a shop might give away its stock in its promotion, but producing these goods would still have required the use of scarce resources, so this would not be a free good in an economic sense.
There are three main types of free goods:
Copyrights and patents have the effect of converting some goods to scarce goods by law. Although these goods are free goods (in the economic sense) once they have been produced, they do require scarce resources, such as skilled manpower, to create them in the first place. Thus these laws are sometimes used to give exclusive rights to the creators of such "intellectual property" in order to encourage resources to be appropriately allocated to these activities.
Many futurists theorize that advanced nanotechnology with the ability to automatically turn any kind of material into any other combination of equal mass, will make all goods essentially free goods, since all raw materials and manufacturing time will become perfectly interchangeable.