"The difference between Linux and Windows is that the linux
kernel is a continuously (and rapidly) moving target. When somebody
probes for Windows 98 or Windows 2000 or Windows Vista, they can be
sure about the behaviour, but Linux is too generic for us. The bug
in one version of the kernel can be fixed in another one, and the
behaviour changes, so one cannot rely on _OSI("Linux") as there is
no generic/constant "Linux" interface.