The Denodo Express license doesn't support generic JDBC connections, so you won't be able to access Marklogic using this license even if you had a JDBC driver to do so. Denodo provides other ways to connect to Marklogic that are also limited by the Express restrictions (like ODBC or developing a Custom connector leveraging Marklogic's JAVA API). However, the Express license does allow to connect to REST web services, so you can access to Marklogic using its REST API (both XML and JSON).
If you need more information about the Denodo full version license, please contact firstname.lastname@example.org or fill the contact form at http://www.denodo.com/action/contact-us/
Hope this helps!