ditto to Chemlak's response and to add...... by definition it is considered "Fair Use"...
The author(s) intent, in this case a roleplay game conveys a "degree" of latitude in the sharing of information.
Another caveat or two, :
1>would be you are not profiting from it (ie financially, obviously you collectively "profit" from your groups participation). Now this, however doesn't imply you can scan images of those books in mass and post them for use by your players, even privately.
Which is why WOC (Wizards of the Coast) could certainly send the "IP Police" your way if you were to copy in mass the Character sheet or the Tokens located in the back of the 3.5edition PHB or DMG. Thankfully they "removed" their IP rights to those pages in mass with the restriction defined at the bottom of the page ("Permission granted to photocopy for personal use only"). They did not do so for ALL pages between the covers.
2>AND acknowledgement of the source material is required in most cases though acknowledgement is not implying that the IP owner can't still protest.
It is for this reason that LWD (ie Hero Lab / Realmworks) may not be contractually licensed to publish some items for a company yet can publish others... ie Piazo is a good example. (though Rob has posted elsewhere they are in constant negotiations with various companies to expand such support). Since LWD profits from the inclusion (and I assume their partners as a pass through licensing cost) they have to be a
great deal more sensitive to the structure of any IP agreements they partner with.
In short, generally companies have opted not to pursue "fandom" (ie supporting literature, art, cartography, etc) that purchasers create, "Fandom" is based on their company IP, but because they realize that it is the very same people that are financing them, they don't often find it financially desirable to pursue such persons. In some excessive cases, it doesn't mean that they couldn't pursue. If they feel that the "fandom" were impacting them financially within their market.
See Here for more info>
http://www.copyright.gov/fls/fl102.html