http://uhden.i2p/articles/systems.html
Apple: Innovation Without Constraints Apple, for its part, has shown that a controlled break with the past
can unlock disruptive advances. With Darwin/XNU, the company is willing
to deprecate old APIs and push developers to modernize applications.
This dynamism yields operating systems that may challenge very old
software, but offer a more modern user experience and a safer, more
efficient platform.