[common; also adj. open-source] Term coined in March 1998 following the Mozilla release to describe software distributed in source under licenses guaranteeing anybody rights to freely use, modify, and redistribute, the code. The intent was to be able to sell the hackers' ways of doing software to industry and the mainstream by avoiding the negative connotations (to suits) of the term “free software”. For discussion of the follow-on tactics and their consequences, see the Open Source Initiative site.
Five years after this term was invented, in 2003, it is worth noting the huge shift in assumptions it helped bring about, if only because the hacker culture's collective memory of what went before is in some ways blurring. Hackers have so completely refocused themselves around the idea and ideal of open source that we are beginning to forget that we used to do most of our work in closed-source environments. Until the late 1990s open source was a sporadic exception that usually had to live on top of a closed-source operating system and alongside closed-source tools; entire open-source environments like Linux and the *BSD systems didn't even exist in a usable form until around 1993 and weren't taken very seriously by anyone but a pioneering few until about five years later.