Please look at the Content Taxonomy Module for a similar, and supported, Drupal 6 alternative to this module.

Taxonomy vocabularies will show up as field types that can be added to content types using CCK. Field types can be named anything you want and you can even have several different fields from the same vocabulary on one content type. Freetagging vocabularies aren't yet supported. Storage is done in the CCK tables only. Basic views and token module integration is provided, and this module handles changes to the 'multiple' setting on vocabularies gracefully. It also cleans up after itself if you delete a vocabulary.

Philosophy of this module

My goal with this module is to leverage taxonomy.module's list and hierarchy building interface to build fields for CCK. In doing this, the intent is to be able to sidestep the whole taxonomy mechanism altogether. One facet of this is being able to get rid of the taxonomy forms on nodes (because they're being replaced with CCK forms). To do this the module makes the content type selection on the vocabulary forms optional instead of required, so that you can now select zero content types for your vocabulary.

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