Hi there,
Vomiting black liquid seems most likely as altered blood though bile may be brownish sometimes as well. It looks like he is in final stage of cancer.
Morphine is a pain killer and if he is not in pain he is unlikely to be started on it. The perception that morphine is given to put someone out of misery, is rather for pain really. Many patients morphine is given short time and is stopped when pain is relieved. Do speak to your hospice nurse and get a clear picture and usually they explain the situation on day to day basis. Regards