D20 System

The d20 System is a role-playing game system published in 2000 by Wizards of the Coast, originally developed for the third edition of "Dungeons & Dragons". The system is named after the 20-sided dice which are central to the core mechanics of many actions in the game.
Much of the d20 System was released as the System Reference Document (SRD) under the Open Game License (OGL) as Open Game Content (OGC), which allows commercial and non-commercial publishers to release modifications or supplements to the system without paying for the use of the system's associated intellectual property, which is owned by Wizards of the Coast.
The original impetus for the open licensing of the d20 System involved the economics of producing role-playing games (RPGs). Game supplements suffered far more diminished sales over time than the core books required to play the game. Ryan Dancey, "Dungeons & Dragons"' brand manager at the time, directed the effort of licensing the new edition of "Dungeons & Dragons" through the d20 System Trademark, allowing other companies to support the d20 System under a common brand identity. This is distinct from the Open Game License, which simply allows any party to produce works composed of or derivative of designated Open Game Content.
Mechanics.
The d20 System is a derivative of the third edition "Dungeons & Dragons" game 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". Tweet, however, stated "The other designers already had a core mechanic similar to the current one when I joined the design team".
To resolve an action in the d20 System, a player rolls a 20-sided die and adds modifiers based on the natural aptitude of the character (defined by six attributes: Strength, Dexterity, Constitution, Intelligence, Wisdom, and Charisma) and how skilled the character is in various fields (such as in combat), as well as other, situational modifiers. If the result is greater than or equal to a target number (called a Difficulty Class or DC) then the action succeeds. This is called the Core Mechanic. This system is consistently used for all action resolution in the d20 System. In prior games in the "D&D" family, the rules for different actions, such as the first-edition hit tables or the second-edition "Advanced Dungeons & Dragons" ("AD&D") "THAC0" and saving throw mechanics, varied considerably in which dice were used and even whether high numbers or low numbers were preferable.
The d20 System is not presented as a universal system in any of its publications or free distributions, unlike game systems like "GURPS". Rather, the core system has been presented in a variety of formats that have been adapted by various publishers (both Wizards of the Coast and third-party) to specific settings and genres, much like the "Basic Role-Playing" system common to early games by veteran role-playing game publisher Chaosium.
The rules for the d20 System are defined in the System Reference Document or SRD (two separate SRDs were released, one for "D&D" 3rd edition and one for edition 3.5), which may be copied freely or even sold. Designed for fantasy-genre games in (usually) a pseudo-medieval setting, the SRD is drawn from the following "D&D" books: "Player's Handbook" v3.5, "Expanded Psionics Handbook", "Dungeon Master's Guide" v3.5, "Monster Manual" v3.5, "Deities and Demigods" v3.0, "Unearthed Arcana", and "Epic Level Handbook". Information from these books not in the SRD include detailed descriptions, flavor text, and material Wizards of the Coast considers more specific product identity (such as references to the Greyhawk campaign setting and information on mind flayers).
d20 Modern has its own SRD, called the Modern System Reference Document (MSRD). The MSRD includes material from the "d20 Modern Roleplaying Game", "Urban Arcana Campaign Setting", "d20 Menace Manual", and "d20 Future". The MSRD can cover a wide variety of genres, but is intended for a modern-day, or in the case of the last of these, a futuristic setting.
History.
Development.
Ryan Dancey believed that the strength of "Dungeons & Dragons" was in its gaming community instead of its game system, which supported his belief in Skaff Elias's axiom known as the "Skaff Effect" which suggested that other companies only enhanced the success of the RPG market leader, which was now Wizards of the Coast. Dancey also theorized that the proliferation of game systems weakened the RPG industry, and these beliefs led to the idea to let other publishers create supplements for "D&D". This led to a pair of licenses released by Wizards in 2000, prior to the release of third edition "D&D": the Open Gaming License (OGL) made the "D&D" third-edition mechanics permanently open and available for use as a set of system reference documents, while the d20 Trademark License built on this by letting publishers use Wizards' official "d20" mark to show that their products were compatible. Unlike the OGL, the d20 License was written so that it could be cancelled at some point in the future.
2000–2003: d20 boom.
Initially there was a boom in the RPG industry caused by the d20 license, with numerous companies producing their own d20 supplements. Some companies used the d20 system to try to boost the sales of their own proprietary systems, including Atlas Games and Chaosium, while many more publishers exclusively produced d20 content, including older companies such as Alderac Entertainment, Fantasy Flight Games, and White Wolf, as well as new companies like Goodman Games, Green Ronin, Mongoose Publishing, and Troll Lord Games. The success of the d20 license helped to launch the RPG PDF industry; there was a demand for d20 products, and electronic delivery offered players a very quick and cheap way to distribute content.
Wizards also began using their new d20 system for more than just fantasy games, including the "Star Wars Roleplaying Game" (2000) and the "d20 Modern Roleplaying Game" (2002). Wizards developed one of "d20 Modern"'s settings into a full sourcebook: the "Urban Arcana Campaign Setting" (2003), and extended d20 even further with the science-fiction "d20 Future" (2004) and the historical "d20 Past" (2005), then closed out the "d20 Modern" line in 2006 with another campaign setting, "Dark•Matter". Third-party publishers used these d20 genre books as the basis of their own campaign settings; too. For example, White Wolf used the "d20 Modern" rules to publish a licensed version of "Gamma World" (2006) as well as a few supplements.
2003 onward: 3.5 edition and d20 bust.
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 to require that publications 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.
At Gen Con 36, in August 2003, Wizards published an updated version of "Dungeons & Dragons", edition 3.5. Third-party publishers had very little warning of the update and so many companies were stuck with books that were out-of-date before even reaching their audience. Wizards did not offer any update for the d20 trademark. Exacerbating the problem, the market was suffering a severe glut of low-quality material published under the D20 label, as many publishers, both petty and established, rushed poorly-written adventures and expansions to print to try to take advantage of d20's popularity, ultimately devaluing the brand's value among consumers. Between these two crises, many d20 publishers went out of business or left the field, but most of those who remained abandoned the d20 trademark entirely, publishing instead under the OGL. Publishers realized that they could publish d20 games that did not depend upon Wizards of the Coast's core books, and publishers even began to create direct competitors to "D&D" using the OGL.
Trademark license.
Because "Dungeons & Dragons" is the most popular role-playing game in the world, many third-party publishers of the 2000s produced products designed to be compatible with that game and its cousin, d20 Modern. 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. This was known as the d20 System Trademark License (d20STL).
The d20STL required publishers to exclude character-creation and advancement rules, apply certain notices, and adhere to an acceptable content policy. D20STL products were also required to clearly state that they require the core books from Wizards of the Coast for use. All d20STL products also had to use the OGL to make use of d20 System open content. However, products that only use the OGL are not bound by these restrictions; thus publishers were able to use the OGL without using the d20STL, and by including their own character-creation and advancement rules allow them to function as complete standalone games.
With the release of the 4th edition of "Dungeons & Dragons" in 2008, Wizards of the Coast revoked the original d20STL, replacing it with a new license specifically for D&D, known as the Game System License. The terms of this license are similar to the d20STL, but there is no associated OGL or Open Content, and the 4th-edition SRD merely lists the items and terms which may be used in licensed products. This did not affect the legal standing of the OGL, and products based on the SRD may still be released under the OGL alone.
Criticisms.
Unlike the OGL, the d20STL is revocable and is controlled by Wizards of the Coast. Wizards of the Coast has the ability to alter the d20 System Trademark License at will, and gives a short, 30-day "cure period" to rectify any issues with the license before termination. These changes apply retroactively to all material published under the d20 System Trademark License.
"Book of Erotic Fantasy" and 2003 change.
When gaming company Valar Project, under former Wizards of the Coast brand manager Anthony Valtera, 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." This subsequently prevented the book's publication under the d20STL. Wizards of the Coast said this was done to protect its d20 System trademark. The "Book of Erotic Fantasy" was subsequently published without the d20 System trademark under the OGL. Other books subsequently published under similar circumstances include Skirmisher Publishing's "Nuisances", which includes on its cover the disclaimer "Warning: intended for mature readers only."
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. This was perceived as being aimed at the same Valar book; early mockups of the cover had the words "Dungeons & Dragons" in the above text printed much larger and in a different font from the rest, right at the top of the front cover. This could have made the book appear to be an official "D&D" publication to a casual or uninformed observer. The published version does not have that text on the cover.
Other criticisms.
Criticism is also levied at the conditions for termination of the d20 System Trademark License through a breach of its terms. The license requires that, upon breach of the terms of the d20STL which includes any subsequent modifications of the license after publication of a work using the d20 System trademark, all inventory and marketing material must be destroyed. Adhering to the breach conditions is an onerous task for smaller game companies. The mere threat of this condition being imposed was a huge blow to the now defunct d20 System publisher Fast Forward Entertainment, which had released several books that used non-open Wizards of the Coast content due to company president Jim Ward's misunderstanding of the license.
Other criticism is concerned with the part of the d20 System Trademark License which defines "Open Game Content" to include game mechanics, and purports to license it. It is generally held that game mechanics cannot be copyrighted in the United States. According to a circular on the US Copyright Office's website: "Once a game has been made public, nothing in the copyright law prevents others from developing another game based on similar principles."
One result of this has been the abandonment of the d20 System License by some publishers in favor of a simple "OGL" designation. Mongoose Publishing's licensed games based on the Conan the Barbarian property ("") and the Robert A. Heinlein novel "Starship Troopers", for example, use systems that function nearly identically to d20 but do not carry the d20 logo.