It is a longstanding practice that software researchers share their source code with the research community, llowing other researchers to inspect their work and to build on it. Many widely used software systems originated as code distributions from research projects. Early examples include Berkeley Unix, sendmail, T E X, Emacs, and many others. The distribution practices of the research community evolved into the free software movement initiated by Richard Stallman, and the more recent open source and libre software movements. Eric Raymond has rgued eloquently in “The Cathedral and the Bazaar ” that the development processes that stem from these pproaches to software development and distribution lead to higher quality software than the traditional proprietary approaches. There is much talk about open source in the commercial arena. In this paper we review the issues that surround the open source pproach to software development. We consider the impact of open source on industry, on government, and on the research environment from which it emerged.