This is a placeholder project to prevent other projects from claiming the namespace "theme", potentially wrecking havoc with your Drupal site.
README.txt
There are a lot of placeholder functions in Drupal called theme_[element]. These are called whenever something called [element] is going to be themed, usually by using the theme('[element]', $variables) function.
The theme() function looks for modules, themes, theme engines who wants to theme the element in question, and uses the most specific choice available. If no valid choice is available, it will fall back to the theme_[element] function, which should be declared by Drupal core or the module introducing the element in question.
If your website were to have a module called "theme", Drupal could end up being utterly confused about the theme_[element] function, since modules replace these fallback functions by declaring an own function with the name [modulename]_[element]. When modulename is the same as the fallback name, strange things may happen.