Thousands I guess. Take Wordpress for example. Didn't it change the world? Take PHP itself, or Perl. Didn't they?

Also, I think the phrase "change the world" is overrated. Sometimes it's not less important to keep the world running, which also requires constant work and a lot of human genius.

You seriously don't think Linus is solely responsible for Linux, do you?

He should and does get the credit for having the insight and chops to have started it all, and is the single-most important person for Linux, but today's Linux is the result of the work of thousands of programmers.

rms, jwz, Guido, Matz, DHH, Shuttleworth, even Rasmus, the many contributors to GNU, gcc, Firefox...

Imagine the software landscape as it would be right now with no free software whatsoever. Then imagine the hundreds of brilliant people required to devise and lead each of those projects...

What about Richard Stalman (before Linus), the Apache Group (before Linus) and Mozilla? And I am pretty sure there are plenty more examples.