The mechanics of original and basic D&D.
Typically Open Game License.
- Adventurer Conquerer King System ● 'Autarch's Adventurer Conqueror King System fulfills the promise of the original fantasy role-playing game by providing comprehensive, integrated support for play across all levels of a campaign.'
- Backswords & Bucklers ● Fantasy dungeoncrawling in Elizabethan England.
- Basic Fantasy Role-Playing Game ● A fusion of Basic D&D with D&D 3E to create a simple, light-weight game.
- Dangers & Dweomers ● A merger of Swords & Wizardry and Basic Fantasy.
- Dark Dungeons ● A tabletop RPG based on the Rules Cyclopedia.
- Dark Passages ● A modern fusion and re-organisation of 0E and 1E rules.
- Darker Dungeons ● A tabletop RPG based on a streamlined version of the Rules Cyclopedia.
- Darkest Dungeons ● A mash-up of the Rules Cyclopedia and Rolemaster.
- Epées & Sorcellerie ● A game inspired by Original Dungeons & Dragons with some modern changes.
- Labyrinth Lord ● A retroclone of Basic/Expert D&D.
- Lamentations Of The Fire Princess ● Weird fantasy role-playing.
- Mazes & Perils ● 'Mazes & Perils is a game of imagination and role playing in a fantasy world, suitable for ages 10 and up.'
- Mutant Future ● Post-apocalyptic role-playing compatible with Labyrinth Lord.
- Project 74 ● A rules-lite game that works only in conjunction with early editions of Dungeons & Dragons
- Spellcraft & Swordplay ● A retro role-playing game that combines Chainmail and Original Dungeons & Dragons.
- Star Blades ● Science fiction role-playing using the original Dungeons & Dragons rules.
- Swords & Wizardry ● A retroclone of original and whitebox Dungeons & Dragons.
- Tales of the Grotesque and Dungeonesque ● Horror role-playing resource.
- The Big Brown Book ● A take on 0E D&D that avoids using d20s altogether.
- Torch & Sword ● A retroclone of 0D&D.
- Wrack & Wruin ● Ryan St's rewriting of original D&D in the style of Apocalypse World.