Does this only work with Drupal?

Yes, all of our site templates are varieties of Drupal. 

You can also share your own Drupal apps / sites / recipes / distros through Drupal Forge. 

Since the underlying platform is language/app agnostic, you can also create decoupled/headless apps and sites.

However, the mission of this project is to support the Drupal community so all apps offered here will be designed to work with Drupal.