Does macOS ship with software developed by third parties? I know in the days of Classic Mac OS, Apple had a habit of shipping the OS with pieces of software, often useful little utilities, that while on the face of it look like any other piece of bundled software, are actually written by third parties and simply paid for by Apple to be able to be included with every installation.

Is this practice still followed? To clarify, I don't mean software written by a company which is then bought out by Apple and their software shipped; but software written by a company which remains independent, but is shipped with Mac OS.
In short, yes.

Apple is built upon Open Source technologies.  

Familiar projects like Apache, Bash, CUPS, PostgreSQL, OpenSSH, Python, Xorg, and Zlib are all parts that make up macOS. For a full list, see the link above.


  Open Source software is at the heart of Apple platforms and developer
  tools, and Apple continues to both lead and make significant
  contributions to many Open Source projects. Major components of Mac OS
  X, including the UNIX core, are made available under Apple’s Open
  Source license, allowing developers and students to view source code,
  learn from it and submit suggestions and modifications. In addition,
  Apple uses software created by the Open Source community, such as the
  HTML rendering engine for Safari, and returns its enhancements to the
  community.


Even the underlying core OS is comprised of third party technologies - FreeBSD for the kernel, filesystem, and networking.



(This is one of the reasons, I left Linux and went FreeBSD - there's a great deal of portability between macOS and BSD)