I searched for CLASS_TYPE_ARTIFICER constant in all prc scripts. There are some entries in crafting system:
prc_include\prc_craft_inc.nss
prc_include\prc_x2_craft.nss
prc_scripts\prc_craft.nss
in the function that check crafting feat prerequisites (prc_scripts\prc_enforce_feat.nss) and a code for UMD check (spells\x2_pc_umdcheck.nss)
The class is not hooked to EvalPRCFeats() function = class specific feats were not coded (i think). I don't remember what feats does artificer gain, I'll get back to you when I check that ;p
Edit:
Artisan Bonus = the code in UMD check
Item Creation = the code in crafting system
Artificer Knowledge - it's probably impossible in NWN (magical aura?), I would suggest making something like Bardic Knowledge feat.
Craft Reserve - seems easy to code, but will require a hook to crafting system (if it's not there already)
Disable Trap - we could use Trapfinder feat from Beguiler.
Craft Homunculus - difficult :/
Retain Essence - something like magical electrifier from SoU but instead of adding charges it would add xp to craft reserve pool.
Metamagic Spell Triger/Completion - I've added something similar to Hellfire Warlock class
Skill Mastery - iirc warlock has similar ability but only for UMD checks (not sure where spellcraft checks are made :/ )
Infusions - the most complicated part ;p