Linux brought a large new demographic (hobbyists, students) to Unix at a time that it was expensive, little used and dying. The Linux movement, as opposed to the Linux software, was a true revolution and not easily replaced. Effective movements are a lot harder to build than effective software.
Another counterexample would be the internet itself. It could very easily have gone wrong and we would have been stuck with the likes of Compuserve and AOL.
In the article: "When we see extremely skewed demographics, we have very good reason to suspect that something is wrong with our selection process"
In my chess club have the same kind of female/male ratio: 12 females on 220 members. Leaving out the youth members it is 8 out of 180 or about 4% ;-) Something must be wrong with our non-existent selection process.
Another counterexample would be the internet itself. It could very easily have gone wrong and we would have been stuck with the likes of Compuserve and AOL.