collective.behavior.vat provides VAT related behavior to dexterity content types.
The behavior can be added through the web or directly through the file system to the dexterity content type xml file like:
<property name="behaviors"> ... <element value="collective.behavior.vat.interfaces.IVAT" /> ... </property>
You may list collective.behavior.vat to buildout.cfg or setup.py in your own package.
Use zc.buildout and the plone.recipe.zope2instance recipe by adding collective.behavior.vat to the list of egg:
[buildout] ... eggs = ... collective.behavior.vat
You may also list to install_requires to setup.py within your package.