Two projects claim to do this already: 

 * [https://sourceforge.net/project/showfiles.php?group_id=108268&package_id=116868&release_id=236821 Sesame-Jena Adapter] 
   * A SAIL for Jena model. (i.e. access Jena through sesame api)
   * Last release May 8th - 2004. 
   * 3122 lines of code

 * [http://www.ecs.soton.ac.uk/~wf/jsm.htm Jena Sesame Model] 
   * A wrapper for a Sesame Repository, conforming to Jena Model and Graph interfaces. 
   * Last release: July 2005 
   * (Claims to) work with Jena 2.2 and Sesame 1.2
   * Does not pass included JUnit tests...
   * 1869 lines of code.

We need:
 * Something that works with Sesame 2
 * Sesame Repository -> Jena Graph 
 * Jena Model -> Sesame repository

Should we just reimplement? A highly scientific counting of lines of code tells me: 3122 lines for JenaSail and 1869 for JSM...