FreeBSD is a free, open source operating system developed by the FreeBSD Foundation. It has been in development for over 20 years and can be used to power desktops, servers and embedded platforms. It is seen as an alternative both to commercial operating systems like Windows, as well as free alternatives like Linux.
Why choose it?
FreeBSD sets itself apart from the competition by being entirely free for both personal and commercial use. Its code is completely open source, meaning anyone can edit it as they like and they are also free to share their code revisions as they wish. Though home use is somewhat limited, it is a popular choice for servers and enterprise level hardware, with many large technology companies such as Cisco, Sony and McAfee all using it in some way.
FreeBSD is a very popular choice for server architecture because the code base is completely open and it can be modified to suit the user's explicit purpose. In addition to this, due to its age, it already has many robust software packages that developers can import to use on their existing projects, thereby reducing their work load.