The author says he wrote it to "experience the construction of a Classic Dungeons & Dragons retroclone". If that is the standard he's measuring himself against, it's probably a failure, because it strays too far from it's source material to be a clone. As a game inspired and obviously building upon OD&D, I think it probably succeeds. It certainly looks quick and easy to play.
It's does not use the OGL and is instead released by the author into the Public Domain. Not sure how that works but it's a nice gesture.
From the blurb:
Yet another retroclone, Dungeon Raiders simplifies Original D&D and early D&D into one straightforward fantasy RPG system. Included are stats, rules, and spells for characters up to level 3, and it'll probably take you a while to get there.
Includes art by Jared von Hindman