For those interested in the unique legal issues surrounding the licensing of spatial data, I recommend you check out the following discussion associated with the OpenStreetMap Project: http://wiki.openstreetmap.org/index.php/Legal_FAQ.
Most of the contributors are spatial data users, rather than lawyers, so it is very practical. The questions and discussion focus primarily on issues associated with the licensing of open spatial data. However, many of the issues, such as copyright, what constitutes a derivative product, and the combining of spatial data from various providers. are prevalent throughout the industry.