You did know the the "No Such Agency" of the US gov has a security enhanced version of Linux, didn't you? Complete with source code, research papers and methodology. And "anyone" can download it.
I suspect they might even run it on some of their supercomputers.
The horror.
Of course I know, and it's a complete outrage, and why I am making a point to let others know. What's amazing is that people like you don't see anything wrong with it, and could care less if OBL created his own free version called OBLinux and used it to design nuclear bombs to attack the US with. You could obviously care less, so long as you keep getting those free copies yourself.
Not to mention that various individuals have repackaged them for major distributions (e.g. Fedora/Red Hat, Debian, Slackware, Ubuntu, Gentoo, SuSE.)
Even Fermilab puts out its own distribution of Linux based on RHEL source RPMs.