I have done it! It seems that the contents of the microSD have been executed without failures. Now it shows a black screen with the following text:

INIT: version 2.86 booting
INIT: Entering runlevel: 5

Angstrom

The Openmoko Distribution -- powered by Angstrom (none) tty1

openmoko -20090601 (none) tty1

(none) login:

And after a while it shows the following message:

INIT: id "S" respawning too fast: disabled for 5 minutes