collective.behavior.salable provides behavior to switch dexterity content types salable.
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.salable.interfaces.ISalable" /> ... </property>
You may list collective.behavior.salable to buildout.cfg or setup.py in your own package.
Use zc.buildout and the plone.recipe.zope2instance recipe by adding collective.behavior.salable to the list of egg:
[buildout] ... eggs = ... collective.behavior.salable
You may also list to install_requires to setup.py within your package.