"This paper reviews our understanding of the growing open source movement. We highlight how many aspects of open source software appear initially puzzling to an economist. As we have acknowledge, our ability to answer confidently many of the issues raised here questions is likely to increase as the open source movement itself grows and evolves. At the same time, it is heartening to us how much of open source activities can be understood within existing economic frameworks, despite the presence of claims to the contrary. The labor and industrial organization literatures provide lenses through which the structure of open source projects, the role of contributors, and the movement's ongoing evolution can be viewed"--National Bureau of Economic Research web site.