In order to show the gist of free software let us outline its’ main features:

• Free software is available at no cost
• You can copy, use, explore, change and extend it without restriction
• You have the same rights concerning this software, as its’ producer
• You can use it in commercial purposes, create and distribute modifications and add-ins and sell them

In practice, for a software product to become a piece of free software, it should be registered under license, saying that the copyright holder permits the aforesaid actions. Also the source code of the program will become available. The customer may be charged for obtaining such features as technical support, training, validation, etc.