Free and open source software has transformed from what has been characterized as a resistance movement against proprietary software to become a commercially viable form of software development, integrated in various forms with proprietary software business. In this paper we explain this development as a dependence on historical formations, shaped by different ways of justifying the use of open source during different periods of time. These formations are described as arrangements of different justificatory logics within a certain time frame or a certain group of actors motivating the use of free and open source software by referring to different potentialities. The justificatory arrangements change over time, and tracing these changes makes it easier to understand how the cultural, economic and social practices of open source movements are currently being absorbed and adopted in a commercial context. © IFIP International Federation for Information Processing 2011