Known error: "Run Shell Script" error. It has been fixed, please download the current version.
MacModder has been designed to make modding easier, something that hasn't been widely available on Macs. Since we launched as Minecraft's first Mac-only mod installer in January 2011, we've been trying new ways to make modding easier. With the constant updates to our software, we've now made it as easy as drag-and-drop installation since MacModder 5.
Now, get ready for MacModder 6!
We've taken a good look at everything you've suggested, and have rewritten the program nearly from scratch to give you a great, easy-to-use mod installer. One small program is all you'll need to get your mods installed now. Simply run the Mod Installer, then drag your mod files in to the folder. Simple!