With the next release (0.1.5), I am introducing the ability to generate PDF files. To do this, gramps is relying on another package. The package is ReportLab, which can be downloaded from www.reportlab.com. It is a GPL package written in Python. If ReportLab is not installed, gramps will continue to operate as usual, but you will not be able to directly generate PDF files (the PDF selection will be greyed out).
ReportLab was an easy choice. Gramps does not require it to run, but installing it gives additional functionality. The big question is in other areas. In particular, the Python Imaging Library would give us significantly more power in handling images (scaling, converting, including images in PDF files, etc) and would reduce the dependancies on external programs such as Imagick. Adopting this would make it a hard requirement on the library, which can complicate installation.
What's the general opinion?