Ghostscript was used in QPS 7.31 for generating thumbnails and previews of PDF files. This is no longer the case with QPS 7.4, 7.5, and 8.x, where the JAWS engine is used to generate thumbnails and previews for PDF, EPS, and AI files.

More Information:
No, Ghostscript is not released with the QPS software. However you can download this software from the following location:
http://www.ghostscript.com/. However, a better answer is to simply update to QPS 7.4, 7.5 or 8.x.