Well calling the server dumb won't get you very far but here is a fun fact for you the base NWN game is what put the alignment restriction on the class not HG and to remove that restriction would require a client side hak which would end up required to log into the server.
Standard game rules have some alignment specifications in order to take levels in them...
Assassins must be evil Paladins must be lawful good Black Guards must be evil Monks must be lawful Barbarians must be non lawful Bards must be non lawful Druids must be neutral Champion of Torm must be non evil Dwarven Defender must be lawful Harper Scout must be non evil Pale Master must be non good
These are all standard NWN game "rules"...we're not just picking on Assassins by having them restricted.
I do not understand what you said, I think that also was not able to express myself ... nwn game in single player, according to the quest that you make you change your alignment ... I wonder how do I change my alignment on the server ... ex: I am true neutral and I have to make to become evil assassin