What is this theme and why is it here?
This theme will be the official back-port of the theme-related work done in the Drupal 8 HTML5 initiative. We want everyone to be able to preview what's coming in Drupal 8 from a markup and CSS perspective. We want anyone to be able to easily review our progress without needing to create another install of an unstable, or unfamiliar version of Drupal.
How it is being developed?
For each theme-layer related change committed to Drupal 8, we'll attempt to implement a Drupal 7 version of that change, here in this theme. We'll track template files, theme functions and CSS files and anything else that is worthwhile and easy to implement in a theme. This won't be possible in every case, but we'll try our best.
Should I use this theme?
No. The purpose of this theme is for you to preview and track the progress of the HTML5 initiative. Over the next couple of years, this theme will be a constantly moving target and there will never be an official release, and it will not be supported like typical themes.
While you shouldn't use this theme for any serious project, you may want reference it. There will be lots of HTML5 and CSS improvements, that you might be interested in, and unless you are a certified theming ninja, you'll probably learn from it.
Get Involved with the HTML5 Initiative
If you're interested in helping with the HTML5 Initiative, we'd love to have you on the team. Here are some links to get you started: