Scripts execute within the context of your character, which means that your character must have the associated skills and resources to execute certain script commands. Therefore, you can't just code yourself 'god items' without having all the necessary prerequisites.
Topia Online lets users script their own spells/abilities with Javascript. Here is an example: http://i.imgur.com/Uawcq.png
Of course, all of the functions/properties are only executed if the caster has the neccessary magic power and reagents. We've balanced this by adding costs to invoking any of the skills and powers.