SELinux is not a distro. It's an Linux Security Module (Mandatory Access Control thing) that comes with the upstream kernel that sysadmins need to STOP TURNING OFF: http://stopdisablingselinux.com

There are alternatives though. SELinux was designed for big machines with multiple physical users. You can use it with pretty much any scenario (and Android uses it for sandboxing apps), but AppArmor is much easier for common personal desktops and web servers.

On FreeBSD and Darwin, the similar thing is TrustedBSD: http://www.trustedbsd.org/mac.html