Although continuous integration starts in proprietary software, it's been present in Free Software for at least decades. Netscape may well be the second or third medium-large software outfit to do continuous integration the way it's done today (we know Microsoft had a team doing this by hand every single day for Windows NT but that's completely insane) because some of its team had experienced this approach elsewhere and knew they needed it if they wanted to ship software that actually works. When Mozilla was created, Tinderbox (that system) along with the Mozilla browser (and so today Firefox) and Bugzilla (a bug tracker) were freed.

I know it probably seems like last week, but that was more than twenty years ago.