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 &