The module file drush_ctex_bonus.module is harmful, and should be removed. The existence of this file causes two undesirable effects:

1. `drush dl drush_ctex_bonus` downloads this project to sites/all/modules instead of $HOME/.drush. When this project exists in sites/all/modules, it must be enabled before Drush will run it. In a global location, it can be used without being enabled.

2. With the module file, drush_ctex_bonus is listed as type drupal-module in packagist.drupal-composer.org (c.f. drupal/drush_ctex_bonus. Without the module file, its type would be correctly listed as drupal-drush. This would allow Composer-managed sites to install this to sites/all/drush instead of sites/all/modules, where it goes today.

Was there any particular reason that this file was added to the project? I think it would be better to take it out, and try to find other solutions to whatever needs are currently being met by this file.