There are a couple of important points to consider in the doc info fields: 1) Scribus supports an initiative called the Dublin Core Initiative. Dublin Core, for short, is a set of specification on document meta-data. 2) The other feature is the fields on the first tab are used in PDF export, as well as also being part of Dublin Core meta-data. This data can be used by special indexing servers which can index PDF files, as well as Acrobat Reader. The second tab contains meta-data in Dublin Core form which can also be used for using a database to track Scribus files.
The second tab is document info which is strictly Dublin Core, thus defined by the specifications:
Publisher | The person or organization responsible for making the document available or for putting into print. |
Contributors | A person or organisation responsible for making contributions to the content of the document |
Date | A date associated with an event in the life cycle of the document, in YYYY-MM-DD format, as per ISO 8601 |
Type | The nature or genre of the content of the document, eg. categories, functions, genres, etc |
Format | The physical or digital manifestation of the document. Media type and dimensions would be worth noting. RFC2045,RFC2046 for MIME types are also useful here |
Identifier | An unambiguous reference to the document within a given context such as ISBN or URI |
Source | A reference to a document from which the present document is derived, eg. ISDN or URI |
Language | The language in which the content of the document is written, usually a ISO-639 language code. Optionally suffixed with a hyphen and an ISO-3166 country code, eg. en-GB, fr-CH |
Relation | A reference to a related document, possibly using a formal identifier such as a ISBN or URI |
Coverage | The extent or scope of the content of the document, possibly including location, time and jurisdiction ranges |
Rights | Information about rights held in and over the document, eg. copyright, patent or trademark |