The OpenBSD project produces a FREE, multi-platform 4.4BSD-based UNIX-like operating system. Our efforts emphasize portability, standardization, correctness, proactive security and integrated cryptography.
* OpenBSD runs on many different hardware platforms.
* OpenBSD is thought of by many security professionals as the most secure UNIX-like operating system, as the result of a never-ending comprehensive source code security audit.
* OpenBSD is a full-featured UNIX-like operating system available in source form at no charge.
* OpenBSD integrates cutting-edge security technology suitable for building firewalls and private network services in a distributed environment.
* OpenBSD benefits from strong ongoing development in many areas, offering opportunities to work with emerging technologies with an international community of programmers and end-users.
* OpenBSD attempts to minimize the need for customization and tweaking. For the vast majority of users, OpenBSD "Just Works" on their hardware for their application. Not only is tweaking and customizing rarely needed, it is actively discouraged.... More Info »
OpenBSD is excellent for servers, appliances and network equipment. When you start to appreciate the security, stability and simplicity you may be tempted to try this OS as a desktop environment which turns out to be a very pleasant experience as well. Examples of window managers in OpenBSD 5.9 are GNOME 3.18.2, KDE 4.14.3 and Xfce 4.12.
OpenBSD is also a great environment for developers. For instance Go 1.5.3, Node.js 4.3.0, GHC 7.10.3 and Ruby 2.2.4 are supported in OpenBSD 5.9.
Several solutions developed by the OpenBSD project (see http://www.openbsd.org/innovations.html) has been adopted by other operating systems including OSX, Linux and Windows. OpenSSH, PF, tmux and LibreSSL are some widely adopted solutions.
See ported software on http://openports.se.
Get started on http://www.openbsd.org/faq/index.html.