Taking a step further in coding standards, Drupal allow for easy look and feel changes via custom themes. So it not only allows for how code operates in the back but also how you define the look and feel of any site. This truly is standards personified. The flexibility is limitless in terms of how you can extend the UI experience.
Drupal themes use standardized formats that may be generated by common third-party theme design engines. Many are written in the PHPTemplate engine or, to a lesser extent, the XTemplate engine. Some templates use hard-coded PHP. The inclusion of the PHPTemplate and XTemplate engines in Drupal addressed user concerns about flexibility and complexity. The Drupal theming system utilizes a template engine to further separate HTML/CSS from PHP.
Again this is a standard code and all GIT standards are complied to ensure seamless deployment. Both custom module and theme combine to form a standard deployment template that may or may not couple with Aegir.