This module has been rewritten from scratch and is now distributed with the Drupal6 version of CCK as content_permissions module. Please upgrade.
This module allows admins to restrict access to specific CCK node type fields to by user roles. This is useful if you have a content type that you want to allow some classes of users greater use of- for example, a CCK node may have a field for a link to an external website. Using this module you can allow only registered users to have access to that field to create, update, and now view.
Note: that when you enable this module for a specific field, you must grant view access for users- when you enable it, it strips view access for all users except the root user. If you disable this module, all access is returned to normal.
CCK Field Permissions does not use node_access so it will not interfere with other access control modules.
CCK Field Permissions does not prevent Drupal's search engine from indexing content that a user might not have access to. This is due to how the search engine interfaces with CCK nodes. Idealy this could be fixed by adding permissions into the core of CCK, however I'm not sure that there is significant interest in that.