So what are the requirements for this armor?
I know in the description it says "only a good character can wear this"
so is it just anything neutral good > chaotic good plus the ability to wear heavy armor then?
am I understanding that correctly?

Thanks in advance!

Yes, a character must be of good alignment (either Lawful Good, Neutral Good or Chaotic Good) and proficient with heavy armour in order to equip it.