GNS stands for "Gamism / Narrativism / Simulationism." GNS as a model was developed by Ron Edwards and others at Gaming Outpost and the Forge, working off of the Threefold Model from rgfa and influenced subsequently by Scarlet Jester's GENder Theory. Gamism, Narrativism, and Simulationism are the three categories of Creative Agenda that Edwards and the other developers of GNS deemed most likely to conflict with one another at the gaming table, causing Incoherence. The individual styles have been defined in different ways over the lifetime of the model -- see their individual entries for more details.

The GNS Model has since expanded to be more comprehensive than just the arena of creative agenda, to become what Edwards refers to as "The Big Model". (The larger context of the model is defined on that page.)

Further people have added other interpretations and/or variants of the model, among them Vincent Baker and Ben Lehman.

References:

• System Does Matter by Ron Edwards (1999)
• GNS and Other Matters of Role-playing Theory by Ron Edwards (Dec 2001)
• Simulationism: The Right to Dream by Ron Edwards (Feb 2003)
• Gamism: Step On Up by Ron Edwards (Jun 2003)
• Narrativism: Story Now by Ron Edwards (Feb 2004)
• The Provisional Glossary by Ron Edwards (Mar 2004)