Examples where open source invented something new?

Joel Spolsky makes an interesting observation about open source in his review of the book Dreaming in Code, about the overambitious failed Chandler project (https://www.joelonsoftware.com/2007/01/21/the-big-picture/):

"Open source doesn’t quite work like that. It’s really good at implementing copycat features, because there’s a spec to work from: the implementation you’re copying. It’s really good at Itch Scratching features. I need a command line argument for EBCDIC, so I’ll add it and send in the code. But when you have an app that doesn’t do anything yet, nobody finds it itchy. They’re not using it. So you don’t get volunteers. Almost everyone on the Chandler dev team got paid."

And it seems true, at least for the time it was written - Linux, MySQL, OpenOffice, GIMP, Inkscape, XWindows, Gnome, gcc - all modeled after existing, successful commercial products. Commercial products proved the demand, did the overall design work, UI, conceptual metaphors, etc. - although no doubt they stood on the shoulders of prior commercial and research projects.

Was curious to see what others think - are of examples where a new, influential product type or category of software began as open source? Bitcoin perhaps?