 FreeBSD developers maintain at least two branches of simultaneous development . The <unk> branch always represents the " bleeding edge " of FreeBSD development . A <unk> branch of FreeBSD is created for each major version number , from which <unk> are cut about once every 4 – 6 months . If a feature is sufficiently stable and mature it will likely be <unk> ( MFC or Merge from <unk> in FreeBSD developer slang ) to the <unk> branch . 
