easy enough to do in most languages (assuming they can read your database, I don't know what dbf is?), just read the data from the database and loop through it writing to files. I would say less than an hour's work for a good programmer once the requirements are clarified.
That said, it would make more sense for search engines to use html pages that actually call the data from the database as this will mean they stay up to date without needing to export the data to text files periodically? Why can't the search engines read the product data from the website itself?