Open source software development has become a large stream in overal software development. In the last couple of years, many open source programs were developed. Open source software is developed by community of programming enthusiasts that seek no financial compensation for their work. Final open source software solutions are compilations of source codes from many individuals. The aim of this paper is to discuss justifiability of open source software development. The main questions are, can open source software be as good as software that is developed by professionals? Are computer users actually using open source software and how much? Should people continue to develop that kind of software and are they bringing something new or just making cheap copies of professional software.