That is quite literally how every part of Cocoa was polished. Things such as sidebars, notifications, came from third party libraries, Growl, etc. were all design patterns from the community. Isn't that also how iTunes came to be? Apple trying to acquire the best music players to integrate into its ecosystem? It's somewhat sad to observe what become of apple.
And jailbreaking was a creative source as well until jailbreaking (full, surviving reboots) went away. Yes there is still a sideloading community but nothing like what we were doing with Summer/Winterboard or the hundreds of random tweaks I applied to my phone back then. So many hours spent scrolling through new packages on Cydia.
I wish Apple would see that opening up their platforms actually leads to a better core OS as Apple borrows/steals from the community.