If my character gets a neograft subtype, will he get temporary hitpoints from necrotic weapons? I have included the text from the Splintered Worlds AP Book.
Adding even a single necrograft to a living body causes the recipient creature to gain the necrograft subtype. Abilities, items, and spells that detect or identify undead reveal necrografts (identifying only the augmentations as undead, rather than the recipient creature as a whole).
Creatures with this subtype are also damaged by spells that damage undead, and can be subjected to other undead- specific effects. If a spell or ability that does something other than deal damage would not normally affect such a creature, but does affect undead, the creature can be targeted, but it gains a bonus to its AC and saving throw against the effect equal to 4 – the number of necrografts it has (to a minimum bonus of +0).
Necrotic: A necrotic weapon deals cold damage infused with negative energy. Creatures immune to negative energy (such as the targets of a death ward spell) are immune to the cold damage of a necrotic weapon, and the cold damage of necrotic weapons a ects only living creatures. Undead creatures targeted by a weapon with this property not only take no damage from the cold but also gain temporary Hit Points equal to the weapon’s item level. These temporary Hit Points last for 10 minutes, until expended, or until the undead gains a larger number of temporary Hit Points from a necrotic weapon. A creature can bene t from only one source of temporary Hit Points from a necrotic weapon at a time.
I don't think that's how that works, by RAW. At least, not for living players of the normal PC races.
The players type doesn't change. They're still living creatures (presumably with the humanoid type), not undead. So they take damage from the necrotic weapons (that deal cold damage).
The portions of the necrograft subtype that I think is overruling your reading here is this:
If a spell or ability that does something other than deal damage would not normally affect such a creature, but does affect undead, the creature can be targeted
The necrotic weapon deals damage, so the necrotic weapon temp hitpoints property is superseded by the first bold, it also normally affects their creature type (humanoid) so it's also superseded by the second bold.
I could see an argument if the characters were also protected by a death ward, since that protection would prevent them from taking damage. But it would still normally affect them, so even then I think that your reading (or your player's argument, if this is something they're asking for) is a little in the realm of wishful thinking.
This is just my opinion though, I'm sure you'll eventually hear 10,000 different ones from 1,000 other people. If you're running it, it's your game, so yours is the only opinion that really matters. If you're playing, your DM's is the only one that really matters.