Sailfish OS (also styled as SailfishOS or abbreviated to SFOS) is a mobile operating system combining the Linux kernel for a particular hardware platform use, the open-source Mer core middleware, a proprietary UI contributed by Jolla, and other third-party components.
Sailfish is developed by Jolla, the Sailfish and Mer project communities, corporate members of the Sailfish Alliance and various open community members. The operating system software is Open source with added closed-source components and extensions of third parties which may come with their respective licenses as well.
The Sailfish community makes development requests and decides development priorities by voting. The Mer project (a free and open-source software distribution, targeted at hardware vendors) receives contributions from the Jolla and its community, as Mer is the source of middleware for Jolla, ensuring the continuous development and compatibility maintenance of both projects.
The OS is shipped with the Jolla smartphone and tablet (discontinued and from other vendors licensing the OS. More or less unofficially the OS is being ported by community enthusiasts to third-party mobile devices including smartphones and tablets.
Sailfish aside from running its native application can run Android application fully except apps built without compliance to the Android development standard of control.
Sailfish OS offers improved Android application compatibility with support for Intel architecture, including the Intel Atom x3 processor. The improved user experience enhancement has produced even richer user interface and multitasking on both smartphones and tablet.
Jolla offers strong privacy and personalization features with its cool UI/UX features like; enhanced notifications and events views as users simply swipe their way to access the main functions.
At the time this post is published Sailfish OS is at Version 188.8.131.52 (released on 23rd Feb) since the initial release of Version 184.108.40.206 (codename: Kaajanlampi) in 2013.
According to Wikipedia; over 30+ devices have been successfully ported to Sailfish with a dedicated community support by community enthusiasts of the Jolla community, XDA and may others.
Through collaboration between Jolla and Sony Open Devices Program, Sailfish OS may become a de-facto OS for the Sony Xperia devices pretty soon. Jala Group, a Bolivian company aiming to make South America technologically independent by investing in Sailfish OS and implementation of it in the region is heavily involved in the development of Sailfish to release Jala’s first Sailfish based device called Accione. Check back soon for a tutorial on how you can install Sailfish OS.
Also Check out Introducing: Jolla Smartphone