DoubleCommand is software for OS X (a kernel extension) that lets you remap keys, in other words change the way your keyboard works. Often used to make a PC keyboard more comfortable with a Mac, swapping the Alt (Option) and Windows (Command or Apple) keys, since they are in swapped positions on Mac and PC keyboards. DoubleCommand is a quick and easy way to fix this if you use a PC keyboard with your Mac. Called DoubleCommand because originally it was used to give the old PowerBooks a second Command key, where there was an enter key.
What's new in DoubleCommand
Support for OS X 10.9 Mavericks, and dropping support for 10.4 and 10.5.