ZombieRoboNinja said:
I'll admit to being very unsure how far copyright extends
copyright typically extends more that 100 years, depending on certain circumstances regarding the work's creation.
trademark extends as long as the company in question continues to pay for it.
patents actually run out pretty quickly, but IARC, they're so expensive and so limited as to be worthless for rpg publishers.
On another note:
It strikes me that WotC has no real reason to restrict their Product Identity to the extent that they did in 3e. Since the GSL prohibits wholesale copying, and is likely to not allow a third publisher to make derivatives of a second publisher's work, then what damage does it do to allow publishers to reference PI monsters, Gods, and locations?
After all, the closer the setting of a 3rd party product is to that of core D&D, the more likely it is to drive up sales of WotC's future books.
For example. Say Necromancer games published an adventure that takes place in the temple of a moon goddess. They could stay generic, and call it "Temple of the Moon Goddess". Or, they could make up their own name, and call it "Temple of Lunora". Or, WotC permitting, they could call it "Temple of Sehanine".
If wizards later puts out a sourcebook called "Secrets of Sehanine", which of those Necromancer adventures is likely to have the best influence on sales?