"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 most important info there is about monsters, their stats and CR, is now color-coded in the tooltips relative to your stats and level.