wget -O bittorrent_sync_freebsd_x64.tar.gz http://download-new.utorrent.com/endpoint/btsync/os/FreeBSD-x64/track/stable
or
wget -O bittorrent_sync_freebsd_i386.tar.gz http://download-new.utorrent.com/endpoint/btsync/os/FreeBSD-i386/track/stable
tar xf bittorrent_sync_freebsd_x64.tar.gz
cp btsync /usr/local/bin