In the market of ERP systems, commercial providers are still leading. Open source products are already introduced in the world of operating systems, web server and content management systems and none want to missing them, but it seems to be difficult to establish them in the ERP products. There are many arguments against an open source product but certainly many for it. One of the weightiest argument is probably the question of warranty. These can be bought as well as in commercial products, in form of license fees and maintenance contracts to most open source products.
The primary aim of the present work is to study, whether a small and medium business company can change to an open source ERP system and work with it. This paper will explain the primary and secondary business processes of an existing small business and the transition to an open source system (OSS) will be examined and identified. A possible transfer of data from a legacy system is examined and the methodology used and their steps will be explained. At the end, there exist a functioning ERP solution, based on OSS, for this company. The business processes should be well documented and made transparent. The advantages and disadvantages of this solution are presented also.