Can I use QTM for websites other than blogs?
Yes or no, depending on your content management system. Some of the less blog-oriented CMSs do not support the posting method QTM uses, at least not enough to support QTM. Examples include Joomla!, although this may change in the near future.
While you can use QTM to post entries to a blog or pages in a taxonomy system in Drupal, you cannot use Drupal's full capabilities. For example, if you are working on a Drupal "book" entry, like this page, you cannot use QTM to decide where in the "book" the page goes. You must do this by using the administration pages on your Drupal website.