All powered by the Linux kernel, the very meaning of monoculture.

Also it isn't as if BSD, FreeRTOS, Aix, INTEGRITY, SmartOS, Illumos, QNX,... don't exist.

But it’s not a monoculture because they’re wildly different applications of the technology.

It’s also not a culture at all because it’s a kernel.

FreeRTOS is an odd one in that set.

It also has good enough POSIX support.

> Aix

This is more a limitation on the architecture - virtually nobody has power arch hanging around to play on.

As owner from Red-Hat and Linux contributor since 1998, IBM isn't certainly blocked by choice, they also have Linux for the same architecture, which Aix customers could switch to and don't.

I mean, AIX essentially _does_ not exist unless you happen to work in an enterprise or are in a similar environment that has it. It's not something to easily get your hands on – esp. not "as a kid".