As BP says, it's obviously OK to do short flights with terminally ill people. I am sure that after all these years some lawyer has had a look into it...
Also, if I am terminally ill, and get discharged from hospital to die at home, I could take up snowboarding or skydiving, for all that anybody cares - so long as I can physically do it obviously. Is the pilot of the dropping plane going to get done if I die while airborne?
The difference is that he may or may not know I was ill, whereas the OP here presumably does know.
So, the only problem I see is the practical one - can the passenger make the journey?
There are plenty of "normal" people I would not do that trip with
