Bukkit

Config file: (If you mess it up, delete it and it will auto regen)
You don't actually ever need to touch this. You can use the commands that are outlined in the commands section entirely!

adopt:
    price: 0.0 # Set this to the number of dollars or items you want
    type: -1 # Set this to a positive integer to use an item, or leave it -1 to use dollars
    limit: 10 # The max number of wolves someone can spawn using the /adopt command
    aggro: friend # Could also be angry or neutral
    worlds:
        world:
            price: 0.0
            type: -1
            limit: 10
            aggro: friend