This basically mean: "yes, I'm allowed to commit those changes to this repository".
WebOS / HP went on and slightly changed clause (d) in order to create its own variant. So if you happen to write:
Open-webOS-DCO-1.0-Signed-off-by: First Last <email@example.org>
you not only declare a certificate or origin, you also grant a specific commercial entity (HP. Not any WebOS non-profit) the right to do whatever it wanted with your code.