The current standard for generating a built distribution is the utilization of Drush and makefiles. Makefiles allow a user to define a specific version of Drupal core and other projects (such as themes, modules, and third-party libraries) that will make up a Drupal code base. It is not a dependency management workflow, like Composer, but is a build tool.

If you take a look at the Demo Framework's profile folder, you will see drupal-org.make and drupal-org-core.make. These are parsed by the Drupal.org packager to compile the code base and package it as a .zip or .tar.gz, like the one you downloaded.

As discussed in the first recipe's There's more... section, you can install a Drupal site through the Drush command-line tool. You can instruct Drush to use a specific installation profile by providing it as the first argument.

The following command would install the Drupal 8 site using the Demo Framework:

    $ cd /path/to/drupal8
$ drush pm-download df$ drush site-install df -db-url=mysql://user:pass@localhost/database

Currently, Drupal.org does not package distributions using Composer, which is why there was an extra step to add dependencies when installing the distribution. Many distributions provide project templates to make scaffolding projects simpler.

For example, the following command will set up a Demo Framework site with docroot as the directory for the web server document root, which contains Drupal 8:

$ composer create-project acquia/df-project df

The project template is available on Acqua's GitHub at https://github.com/acquia/df-project/.

Another distribution, Open Social, provides a template of its own:

$ composer create-project goalgorilla/social_template

The project template is available at https://github.com/goalgorilla/social_template.