I'm 80% sure that would fit in the category of "fair use".
I'm 100% sure that it's fair use.
Here's 3 examples of how this could work with RW:
1) You pick up a copy of Rise of the Runelords and put EVERY WORD in that book, into RW. You make the ties, copy and paste the maps to display to your players, and go, go, go, you use it in your game.
2) You do all of the above, AND you give access to it when the player edition comes out for when they discover info in the game (i.e. reveal info to the players).
3) You do 1 and 2, but you also give it away on the boards or TPB, or email your buddies in your local community a copy of your work.
1 = 100% fair use. Nothing wrong with it, its for private use and you're just showing them maps and things on a second display... Exactly like printing out handouts and maps on paper. RPG companies EXPECT you to do this. It's in the OGL, it's in most RPG copyright pages, and it's how games work. You're 100% clear.
2 = 99.999% sure this is also fair use. Your'e good here. It's no different from 1, except your players have access to it whenever they want, not just when you're showing it to them, EXCEPT that it's only the info you have revealed to them. You're fine.
3 = big no no. Copying everything from a book and passing it out is not going to make you friends at White Wolf, or Piazo, or WotC. The difference between 1&2 and 3 is best explained thusly: You loan a copy of the book in 1&2, you COPY the book and pass it out in 3. No good.
Yes you can do anything you want with realm works for you and your group's useage. you CANNOT copy your database and hand it out to your local GMs for free/money if it's not your own work.
IP laws and gaming are weird, but you essentially have to word for word copy RPG books to violate fair use.