A YAML for Drupal 7.x installation profile with Drupal 7 has been published in the download section. The integrated Drupal core version is patched for YAML with the required core patches.
This package is based on current Drupal core version and contains the current theme versions of
yaml_simple. Additionally it contains some useful modules and two installation profiles that allow a Drupal core configuration with the YAML theme enabled and set as default theme on your new website. The installation profile YAML Standard is based on core Standard installation profile and the installation profile YAML Standard (Localized Drupal) is original based on the great Localized Drupal Distribution installation profile that end with a localized Standard installation. With these multilingual installation profile you can setup Drupal in your beloved language and all module translations are automatically downloaded from Drupal Translations. The integrated l10n_update module makes translation updates via UI extremely easy.
The default region for the search block will be set to Main navigation region automatically. You can alter the settings.php to enable the YAML theme as maintenance theme; if the database is down. See Maintenance page theming / offline for more details about this manual step.
This installer is a great help installing Drupal and YAML together in a very few steps.