Apps similar to X Keyboard Extension (XKB) include Karabiner Elements, which is free and open source. Other options are SharpKeys, KeyTweak, xmodmap and keyszer. In total there are six Key Mapping Tools like X Keyboard Extension (XKB) for Linux, Mac and Windows.
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).
Japan
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.
United States
KeyTweak is a free keyboard remapper for Windows NT/2000/XP/Vista/Win 7. It makes use of Microsoft's Scancode Map registry key to remap your keyboard.
United States
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.
A keyboard remapping tool for X environment written in Python. It's like xmodmap but allows more flexible remappings.
Japan
