Thanks! Helped a lot.
Here is my solution:

#!/bin/sh
(
# nohup does not exist - trap SIGHUP myself
trap "" SIGHUP
# otherwise fbpanel will not get hold
rm .fbpanel/default

source /etc/osso-af-init/osso-gtk.defs
source /etc/osso-af-init/matchbox.defs
echo Theme is $MBTHEME
source /etc/osso-af-init/hildon-desktop.sh stop
sleep 2
source /etc/osso-af-init/matchbox.sh stop
sleep 3
openbox-session &
sleep 10
# source /etc/osso-af-init/hildon-desktop.sh stop
# sleep 2
) >/dev/null 2>/dev/null </dev/null ;

Works with default configuration; a few programs make troubles.
osso-xterm appears in the "System" menu.
microb can be started by typing "browser", but does not show navigation bar.
e-mail can be started by typing "modest showui".