I am trying to integrate pay with amazon to drupal site and had a hello of a time, trying to figure out how to do that. They use namespaces and that is not something so common in drupal 7. So to understand it better, check out this video and this blog post
How to use namespaces and what are they
http://buildamodule.com/video/drupal-8-developer-prep-namespacing-and-a…
How to properly setup namespaces in drupal 7 and combine it with drupal 7 code
http://pixel5.us/node/35
The bottom line is, that you either need to add full path of namespace when instancing object, or set it up with USE on the top of the module file.