Files for Mac can be run immediately on all versions of OS X (Lion, Maverick etc). You just need to uncompress the ZIP archive and move the ".app" file into your Applications folder. Then you can launch the game.
See the Help page for more info.
The man behind Shadow of the Beast, Destruction Derby and Driver
Celebrating Christmas, 700 games and another year of Games Nostalgia
The art of game design has never been so revolutionary