There could be problems with FFI gem and libtcod. But libtcod has a version for OS X, so it's not impossible.

I've tried to replace libtcod with pure ruby astar implementation http://rubyforge.org/projects/ruby-a-star/, but perhaps it's unoptimal, because path finding takes about 0.5s making game unplayable.
I've uploaded version with completely disabled astar to source repo, but i can't check other possible problems because i don't have Mac myself.

Thanks for reply!

Hi all!
I've done a game for a gamedev.ru challenge, and now i've finished english version of it, so decided to show it here.
It was inspired by ruby tutorial, but greatly changed after that (and because rules of contest allows using only own content i replaced it with my own ugly "programmers art").
It's a space shooter with inertial movement control scheme, 10 procedurally generated and destroyable levels to complete and about two thousands of devices to install.
It's pretty hardcore, not to say disbalanced though.
You can see short video of it here: http://youtu.be/meOSzt1pJwQ
I'm using ffi gem and libtcod library for pathfinding (as some radar types shows path to exit) because i'm too lazy to implement A* in ruby. So currently it's windows only.
You can get last version and source code here: https://sourceforge.net/projects/weightlessness/