"A fantasy d20-themed dungeon crawler", to quote DarkGod's comment. Inspired by Incursion by Julian Mensch. Made available under Open Game License. This is a non-profit fan project. No money is made. There are currently only two people working on the mod. However, we have released several beta versions so far.
The newest beta has added the ability to display healthbars on the screen, so that you don't have to mouse over everything to know its life level.