Apple & BSD

"Apple explicitly chose BSD as the base for MAC OS to avoid GPL-licensed code. But, despite this antipathy, lots of companies use Linux, and even contribute to its development."

Apple was shipping an OS over which they wished to retain strict control, GPL software was clearly inappropriate.
Most other companies are shipping something on top of the OS, e.g Oracle's database, Tivo's PVR so the OS is an enabler not the main event.