> I don't know when OSI's definition became mainstream. The first time I heard open source, it meant the same as what you said. Nowadays you have to use a different term for that.

The notion that the phrase "open source" started out with broader definition but was later revised by OSI is itself revisionism.

OSI's definition is important because the phrase "open source" originates with the folks behind OSI—the term did not exist before 1998 when they created it. The phrase resulted from a public awareness effort leading up to the release of the Mozilla code on March 31, because the only alternative that had legs at the time was the FSF's term "free software", which had marketability problems. A few months later, a bunch of those involved in the brainstorming session where "open source" was coined went on to start the OSI as an advocacy group primarily concerned with:

a) marketing the term "open source" to get the public to adopt it en masse

b) advocating for the adoption of open source ideals themselves

To sum up, there has never been a time when "open source" meant something besides how the OSI defined it, except for sloppy usage in instances of someone co-opting the OSI's term but not their definition for it.

(Disagree with whether it's a good definition or not, but telling history and facts wrong is something to be avoided.)