Can you explain to me the whole WOTC/OGL/SRD/D20 Thing?
When 3rd edition came out in 2000, Wizards of the Coast (WotC) also created the Open Gaming License (OGL) . This would allow 3rd party publishers to use Open Game Content (OGC) as long as they followed the rules laid out in the OGL. WotC took most, but not all, of the material in the PHB, DMG and MM and created the System Reference Document (SRD). They declared this to be OGC, which is what the 3rd party publishers initially used. At a later date, WotC added material from the Psionics Handbook to the SRD.
When d20 Modern came out, WotC created the Modern System Reference Document (MSRD) . This contains material from d20 Modern, d20 Future, Menace Manual and Urban Arcana.
When 3.5 came out, WotC created the Revised System Reference Document (RSRD) . This contains material from the 3.5 PHB, 3.5 DMG, 3.5 MM, Expanded Psionics Handbook, Deities and Demigods (not everything in this material was converted to 3.5), Epic Level Handbook (as Deities and Demigods) and a little bit from Manual of the Planes.
Any material that WotC did not place in the various Reference Documents is not available for 3rd party publishers to use. The Red Wizard of Thay did not make it into the RSRD, so PCGen can not include that in our distribution.