Hi,
Directories have originally been designed to ease up reuse of content shared by several applications: for instance, you define a test user and groups directory for development, and then use an LDAP directory for production. Or you define a SQL directory to store the list of "subjects" that can be set on your document, using a csv file, but actually in production you'll be using a view of an existing table in another database (that may be shared by several applications). So there is no fine-grained security model on directories for now, and that is why management screens are restricted to administrators: vocabularies, and vocabulary entries are not documents stored in the repository: you cannot benefit from the security model applying to documents.
That being said, Bruce's post does give you a workaround to make this feature available to other users (members of a given group). If we decided to add this kind of feature to the generic platform, we would probably make this configurable somewhere, but we've been thinking of adding a "profile" of "functional administators" to make it reusable in other situations than vocabularies management (still to define).
Last but not least, if you really need fine-grained security over your vocabularies (and want it to be a real security, not just UI tricks), you can also define document types that will hold your vocabulary definitions, and create widget types that would handle retrieval and display of the vocabulary entries (note that there is also room for improvements around directory widgets). You'll have to make sure these vocabularies are initialized correctly, and are visible to all users who would need them to be displayed in a form. I guess this can done fairly easily on a 5.5 version (or even 5.4.2). Page providers and tag nxu:selectItems could be useful.
Hope this helps.
