Can't download with drush

When downloading with drush,

drush dl wysiwyg_imageupload

It doesn't work -- I get the error:

There is no recommended release for project wysiwyg_imageupload on Drupal 6.x. Ask the maintainer to create a release in order to be compatible with drush and the      [error]
drupal.org security broadcast system. A development snapshot release is sufficient.
An error occurred at function : drush_pm_download