Short answers, pulled from the story.
Three primary designers shaped this new framework: Jonathan Tweet, Monte Cook, and Skip Williams. Richard Baker also contributed significantly to the project alongside Peter Adkison, who served as president at the time.
A player rolls a twenty-sided die to determine success or failure during gameplay. Modifiers apply based on six character attributes: Strength, Dexterity, Constitution, Intelligence, Wisdom, and Charisma. If the total equals or exceeds a target number known as a Difficulty Class, the action succeeds.
Wizards released two licenses in 2000 before third edition Dungeons & Dragons launched publicly. The Open Game License allowed any party to produce works derived from designated content without paying royalties. The d20 Trademark License let publishers use the official mark to show compatibility with core products.
Wizards expanded the system beyond fantasy genres with Star Wars Roleplaying Game in 2000. They later developed Urban Arcana Campaign Setting in 2003 and extended into science fiction with d20 Future in 2004.
In 2008, Wizards revoked the original d20STL upon releasing fourth edition Dungeons & Dragons. A new license called the Game System License replaced it but lacked associated open content.