From publisher blurb:
Swords & Wizardry is the ENNIE award-winning retro-clone of the original 1974-1978 rules for Dungeons & Dragons*, an edition usually called Original D&D or "OD&D."
This is a complete game, with rules for character generation, monsters, magic items, encounter tables -- the whole works. It is non-OGL: the original game is re-created using the creative commons grant from Wizards of the Coast, and will have a third-party publisher license once we decide whether to use the ORC license or a different third-party license.
This version includes several additions and revisions to earlier versions. The "random castles" material is added, morale rules are added, and spell research rules are added. The treasure tables are revamped, and errata from earlier versions is now incorporated into the book.