How to identify all modules hosted on drupal.org that depend on a given module?
As was mentioned above the solution could be parsing info files of all projects hosted on drupal.org. You can use this small tool to facilitate the process of obtaining the codebase of Drupal contributed projects.

Below is an example of searching dependencies for Quiz module.

drupal-project-loader -c 5 -b 7.x -d d7_modules -y &amp;&amp;
cd d7_modules &amp;&amp; ag 'dependencies\[\] = quiz$' -G \.info$ |
sed 's/\/.*//;s/^/https:\/\/www.drupal.org\/project\//' | uniq | sort


The result:

https://www.drupal.org/project/certificate
https://www.drupal.org/project/certify
https://www.drupal.org/project/civicrm_cert_quiz
https://www.drupal.org/project/cloze
https://www.drupal.org/project/course
https://www.drupal.org/project/elms_features
https://www.drupal.org/project/grouping_question
https://www.drupal.org/project/image_target_question
https://www.drupal.org/project/kalvi_core
https://www.drupal.org/project/mark_word
https://www.drupal.org/project/og_quiz
https://www.drupal.org/project/opigno
https://www.drupal.org/project/opigno_pretest_app
https://www.drupal.org/project/opigno_quiz_app
https://www.drupal.org/project/opigno_quiz_import_app
https://www.drupal.org/project/qq_import
https://www.drupal.org/project/quiz
https://www.drupal.org/project/quiz_ddlines
https://www.drupal.org/project/quiz_drag_drop
https://www.drupal.org/project/quiz_evaluation
https://www.drupal.org/project/quizfileupload
https://www.drupal.org/project/quiz_h5p
https://www.drupal.org/project/quiz_progress
https://www.drupal.org/project/quizrubric
https://www.drupal.org/project/quiz_sentence_drop
https://www.drupal.org/project/quiz_share
https://www.drupal.org/project/quiz_userpoints
https://www.drupal.org/project/quiz_voice_answer
https://www.drupal.org/project/quizwebform
https://www.drupal.org/project/simple_mcq
https://www.drupal.org/project/tincanapi