Eldritch (now at Mountains of Madness + Source Release) $

[getter77]

http://www.eldritchgame.com/   $15  Win/Mac/Linux
http://steamcommunity.com/sharedfiles/filedetails/?id=166329180

Eldritch is a first-person action game inspired by roguelikes, immersive sims, and H. P. Lovecraft.

    -Unearth ancient secrets and find your way to freedom!

    -Sneak, fight, and explore strange worlds!

    -Invoke mystical powers to augment your play style!

    -Randomly generated levels provide fresh challenges and opportunities!

    -Unlock shortcuts to jump directly to deeper dungeons!

[getter77]

Mountains of Madness  (Free DLC)

The Mountains of Madness expansion is now available on Windows, Mac, and Linux!

Features:

    -Explore a 10-story dungeon beneath the mountains of Antarctica!
    -Face frightening new monsters!
    -Wield new weapons, powers, and tools!
    -Uncover grave secrets in the depths and live to tell the tale!

Game itself is on sale for the next nigh-2 weeks for $7.50

[getter77]

Source Release as per the bottom of this page:

http://eldritchgame.com/about.html#source

zlib, with the specific license and the rather important detail containing release notes there as well as the direct download---here's to hoping this leads to good things in the future as a result of their stellar gesture of generosity here.