mac os x
BSD UNIX with an eye-candy interface, partly developed by Apple, Inc. The internals of the OS (i.e. the GNU Mach Kernel, the X-Windows System, the shells, the command-line binaries and scripts, etc.) were developed in part by the opensource community, whereas Apple, Inc. developed the high-level APIs and the GUI (both are proprietary).
Mac OS X is a good example of what can happen to any *NIX OS if given enough corporate sponsorship (or if it surrenders its licencing to a corporation).
Words you can keep