Don't display the MOTD when an explicit command is run. (possibly via authorized_keys(5) restrictions), even when a pseudo-terminal has been allocated for the session. In other words, only display the MOTD when the server starts the user's default shell.

#!/bin/sh
exec 2>&1
exec dropbear -d ./dropbear_dss_host_key -r ./dropbear_rsa_host_key -F -E -p 22