Index: addons/openacademy/models.py
===================================================================
--- addons.orig/openacademy/models.py	2014-08-27 10:34:08.531934946 +0200
+++ addons/openacademy/models.py	2014-08-27 10:34:08.527934946 +0200
@@ -25,3 +25,4 @@
     instructor_id = fields.Many2one('res.partner', string="Instructor")
     course_id = fields.Many2one('openacademy.course',
         ondelete='cascade', string="Course", required=True)
+    attendee_ids = fields.Many2many('res.partner', string="Attendees")
Index: addons/openacademy/views/openacademy.xml
===================================================================
--- addons.orig/openacademy/views/openacademy.xml	2014-08-27 10:34:08.531934946 +0200
+++ addons/openacademy/views/openacademy.xml	2014-08-27 10:34:08.527934946 +0200
@@ -102,6 +102,8 @@
                                 <field name="seats"/>
                             </group>
                         </group>
+                        <label for="attendee_ids"/>
+                        <field name="attendee_ids"/>
                     </sheet>
                 </form>
             </field>