Francis Tyers wrote:
Now, I've been told that interwiki links do not have the level of originality required for copyright, many of them being created by bot.
Bot or not, it is a widely held view that (tabular) data extracted from Wikipedia is in the public domain. At least that's what I believe. I'm sorry that I have no sources to cite.
You might want to look at other projects that reuse data extracted from Wikipedia dumps, such as dbpedia.org.
Traditional copyright doesn't apply to extracted data, so the GFDL is not applicable. In various countries, "catalog rights" or "database rights" might be applicable to such data, but that right then belongs to those who compiled the table of data (catalog, database), not to the original authors of articles*. I strongly doubt that you could claim such rights if you just extracted interwiki links from the XML dumps published by the Wikimedia Foundation.
*Similar examples are Bible concordances or scientific cross indexes, for which catalog rights belong to the indexers, rather than to the original authors of the texts.
I am not a lawyer. You might get better answers from Mike Godwin, who can speak for the Wikimedia Foundation.