Introduction
This allows for actors to have a happiness value.
What is Friendship?
From the Bulbapedia page on Friendship
“Friendship (Japanese: なつき度 degree of emotional attachment), also often referred to by fans as happiness, is a measurement of how much a Pokémon loves its Trainer and enjoys being in their care. Friendship affects the evolution of certain Pokémon, the power of Return and Frustration, and the availability of a few in-game items and Ribbons. Certain events increase a Pokémon’s friendship (gaining a level, walking 256 steps) or decrease it (fainting, using herbal medicine).”
Actor/Class/Weapon/Armor/State Notetags
<friendship rate: x%> Adjusts the friendship rate by x%
Skill/Item Notetags
<change friendship: sym> Changes the Friendship by the amount for the symbol
Enemy Notetags
<friendship: x> Specifies the friendship value of the enemy
Script Download
Crystal Engine 
Can you elaborate on this? I don’t really understand what this would do.
You have a friendship value to each actor and enemy. Friendship is a measure of how much a Pokemon likes its trainer in the Pokemon games. The script allows you to set the amounts added/subtracted from friendship when certain conditions are met. You can add your own for items.