Linux by itself is just the kernel. The distributors (Red Hat, Ubuntu, Gentoo, etc..) choose different software packages to include in their releases, but by no means does the Linux kernel block software developers from providing host based intrusion detection/prevention solutions, and even if it did.... developers have the ability to make kernel patches if necessary. The source code is released for the public to use and expand on.
As far as Apple's MacOS, they have a similar build to most distributions of Linux. The kernel is based on the Mach "drop-in" replacement for the traditional UNIX kernel, as well as BSD implementation of UNIX. After the kernel is developed, a lot of the "OS" is then built from popular *nix packages as well as many proprietary Apple software... call it a hybrid if you will.
With Microsoft, everything is closed source and behind locked doors. If they shut out software companies from providing host based security solutions to the general population, you can be sure that there will be a lawsuit. The vendors have no choice other than to work with MS on this (and I don't see how MS has a choice either), because "black hat" techniques would only break the software in the future, as MS releases patches to its OS to close these holes.