FreeBSD NFS server by default only accepts NFS connection arriving from ports > 1024, as a “security” measure. This prevents OSX clients to correctly mount NFS shares, because even if executed with sudo your FreeBSD server will still complain with something like:
kernel: NFS request from unprivileged port
To solve this, the easiest way is to add the -P parameter on the client side, mounting the share with
sudo mount_nfs -P server.address:/path/to/share /path/to/local/directory
The eternal fight between admins and computers 