NomadBSD is described as 'persistent live system for USB flash drives, based on FreeBSD'. There are more than 100 alternatives to NomadBSD for a variety of platforms, including Linux, Self-Hosted solutions, BSD, Windows and Mac. The best alternative is Ubuntu, which is both free and Open Source. Other great apps like NomadBSD are Debian (Free, Open Source), Linux Mint (Free, Open Source), Manjaro Linux (Free, Open Source) and Arch Linux (Free, Open Source).
Sabayon is a Gentoo-based GNU/Linux Operating System designed for speed and ease of use. With the ability to use Gentoos Portage or Sabayons own Entropy system, the ability to compile a program for your needs or simply install a pre-built binary has never been easier.
NetBSD is a free, fast, secure, and highly portable Unix-like Open Source operating system. It is available for a wide range of platforms, from large-scale servers and powerful desktop systems to handheld and embedded devices.
illumos is a free and open-source Unix operating system. It derives from OpenSolaris, which in turn derives from SVR4 UNIX and Berkeley Software Distribution (BSD). illumos comprises a kernel, device drivers, system libraries, and utility software for system administration.