Images, JavaScript, and Flash files that PHP sends to the browser are not affected by the GPL because they are data. However, Drupal's JavaScript, including the copy of jQuery that is included with Drupal, is itself under the GPL as well, so any Javascript that interacts with Drupal's JavaScript in the browser must also be under the GPL or a GPL compatible license.
Academic and corporate clients seeking digital journals or other types of web publications regularly require platforms that support standards-based XML. This tutorial explains how to customize a Drupal implementation to develop publications that enable editors, authors, and users to submit and edit content in standards-based XML, where the standard can be enforced using server-side validation settings. For illustrative purposes, the discussion references TEI XML, the markup standard in widespread use in academia.
"To add CSS or JS that should be present on all pages, modules should not implement this hook, but declare these files in their .info file."
CSS files can be added to a .info file using the following format: