d20 System
The three primary designers behind the d20 System were Jonathan Tweet, Monte Cook, and Skip Williams; many others contributed, most notably Richard Baker and Wizards of the Coast then-president Peter Adkison.
Many give Tweet the bulk of the credit for the basic resolution mechanic, citing similarities to the system behind his game Ars Magica.
The MSRD includes material from the d20 Modern Roleplaying Game, Urban Arcana Campaign Setting, d20 Menace Manual, and d20 Future.
[5]: 287 The success of the d20 license helped create an industry for PDF publishing for role-playing games to fill the demand for d20 products, where electronic delivery presented players with a very quick and inexpensive method to distribute content.
[5]: 292 In response to the sexually explicit Book of Erotic Fantasy (2003) announced by Valar Project for Dungeons & Dragons, Wizards of the Coast changed the d20 license so that publications were required to meet "community standards of decency", prompting Valar to simply remove direct references to Dungeons & Dragons and publish the book under the OGL.
This event, by highlighting that Wizards of the Coast still held wide discretionary power over what counted as legitimate d20 material, made third-party game writers leery of publishing under the d20 license.
[5]: 293 Wizards of the Coast released an updated version of Dungeons & Dragons, edition 3.5 at Gen Con 36 in August 2003.
Wizards of the Coast provided a separate license allowing publishers to use some of its trademarked terms and a distinctive logo to help consumers identify these products.
The d20STL required publishers to exclude character-creation and advancement rules, apply certain notices, and adhere to an acceptable content policy.
When gaming company Valar Project attempted to publish the d20 Book of Erotic Fantasy (BoEF), which focused on sexual content, Wizards of the Coast altered the d20 System Trademark License in advance of publication of BoEF by adding a "quality standards" provision that required publishers to comply with "community standards of decency."
The same round of changes to the license also limited the size at which the text "Requires the use of the Dungeons & Dragons Player's Handbook, Third Edition, published by Wizards of the Coast" (which is required to appear on the front or back cover of most fantasy d20 System products) could be printed, and prohibited making part of it larger than the rest.
