How can I make a read only field  form with node authors' mail address on node edit page? I would like to make a read only field form on a node edit page prepopulated with the e-mail address of the node author.
I tried Markup module but couldn't get it done.
Is there anyway to do this?
see http://drupal.org/project/field_permissions, 
from module description:


  The Field Permissions module allows site administrators to set field-level permissions to edit, view and create fields on any entity.