A few dieties have the death domain and still have no evil alignments allowed, could this be fixed perhaps?

I know osiris has none and he has the death domain.

These are not errors. I'd link some older threads on this topic but my accursed laziness bids me to do something less productive. Regardless, Kelemvor and Osiris, and at least one other, have Death instead of Repose, as Repose isn't available in NWN.

Death domain in NWN covers all aspects of Death, dying, spirits travelling through the fugue plane, etc. Some dieties have dominion of the murder and slaying aspect of Death, some over the travel of the spirits and transition to the afterlife, some are the judges of the dead.

In all, Death domain covers a lot of things according to the dogma of the diety in question. Not all are evil.

Well than I have a question, should a kelemvor cleric summon their death avatar? Seeing as kelemvor doesn't preach undead necromancy ect, wouldn't it be better off to have the avatar for them do something different?

There avatar is an outsider, and won't give you evil points i believe

Each death avatar is modified according to the diety. It is not an evil act to summon it for those neutral/good aligned characters.

For example: Urogalan, the halfling diety of death has a spectral hound that appears. The hound being the symbol of Urogalan.