DoubleCommand is described as 'is software for Mac OS X (a kernel extension) that lets you remap keys, in other words change the way your keyboard works' and is an app in the System & Hardware category. There are more than 10 alternatives to DoubleCommand for Windows, Mac, Linux, BSD and X11. The best alternative is SharpKeys, which is both free and Open Source. Other great apps like DoubleCommand are Karabiner Elements (Free, Open Source), KeyTweak (Free), Microsoft keyboard layout creator (Free) and Key Manager (Paid).
SharpKeys is a utility that manages a Registry key that allows Windows to remap one key to any other key. Included in the application is a list of common keyboard keys and a Type Key feature to automatically recognize most keyboard keys. It was developed in C# using .NET v2.
Karabiner, previously called KeyRemap4MacBook, is a very powerful keyboard remapper for Mac OS X. In addition to simple key remapping, it has special remapping modes like Emacs-mode, SandS-mode (Space and Shift).
Ever wanted to quickly and easily define your own keyboard layout for a language Microsoft doesn't support? Or define your own keyboard layout so you can quickly and easily enter your favorite symbols with a simple keystroke?
The macOS supports an XML-based format for keyboard layouts (.keylayout files). However, modifying keyboard layouts—let alone creating entirely new keyboard layouts, such as for a new script—by directly editing the XML text is tedious and error-prone.
The xmodmap program is used to edit and display the keyboard modifier map and keymap table that are used by client applications to convert event keycodes into keysyms. It is a part of the X.Org project.
PCKeyboardHack can change caps lock key behavior. For example, changing caps lock key to delete Key. PCKeyboardHack can activate International Keys on Non-Apple keyboard. == Utility for the caps lock key and some international keys in PC keyboards.