FreeBSD® is an advanced operating system for modern server, desktop, and embedded computer platforms. FreeBSD's code base has undergone over thirty years of continuous development, improvement, and optimization. It is derived from BSD, the version of UNIX® developed at the University of California, Berkeley. The FreeBSD website has all the information needed (especially the handbook) to install and configure FreeBSD itself.
(The information on the pages linked here is obsolete in various ways) Please see the page on building KDE SC for general instructions. See the page on building KDE SC under FreeBSD for specific information for FreeBSD.