You could have downloaded AutoTileGen 1.0 for Mac from our software library for free. The actual developer of this software for Mac is Pixelatto. The application is included in Games.
From the developer:
AutoTileGen is an automatic tileset generator for 2D game terrains. With three basic input tiles, the program generates a complete tileset (48 tiles) for you to use in your games. The features include slopes, normal map generation, a free autotiling plugin (AutoTileSet) and more.
You may want to check out more software for Mac, such as Nostromo Array or rpgng, which might be related to AutoTileGen.