The term open source software has existed since 1998. Before that, the only people who spoke about open source were in the intelligence community, where open source was a specialist term that referred to publicly available intelligence information.
This usage played a role in inspiring the invention of the term open source software, according to Bruce Perens’s essay “The Open Source Definition” in the 1999 book Open Sources: Voices from the Open Source Revolution. In that sense, open source software is itself an extension of a concept that originally applied to something entirely unrelated to software.
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