Just downloaded Fallout one for Mac, but I can't install it. When I double click the DMG, it opens up, I drag it into the Applications-folder, but when I try to run the file named "Fallout" it tells me the file is broken. I can't get it to run. I'm on the latest update of Mavericks.

Anyone have a solution?

Have you tried using the GoG downloader? Some people reported that worked for their mac issues.

Try re-downloading it. Maybe the file is corrupted somehow.

Make sure that Accessibility options are enabled (the installer would have prompted you to do so, but please check it):
System Preferences -> Accessibility -> [check] Enable access for assistive devices.

Copy the game from the DMG file to the Applications folder again - in case it got corrupted. If that doesn't help, check if the game works when you launch it directly from the DMG file (just double-click instead of dragging the game to the Applications folder).

If nothing helps, try creating a new user account, restart your Mac and log onto that new account. Now, try installing and playing the game. This will allow you to launch the game without most third-party applications that may have caused issues. To create a new account, go to System Preferences - Users & Groups.