Use an AT Vocabulary Manager Vocabulary in a Selection Field
This one's simple. In the Options Vocabulary field on the selection form field's [override] panel, just use something like:
substituting your vocabulary's name for "testVocabulary".python:here.portal_vocabularies.getVocabularyByName('testVocabulary').getVocabularyLines()
This recipe assumes you've installed AT Vocabulary Manager and created a simple or sorted-simple vocabulary. You'll also need to have the rights to edit TALES fields.
