SharpKeys is not available for Linux but there are some alternatives that runs on Linux with similar functionality. The best Linux alternative is Input Remapper, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 10 alternatives to SharpKeys and five of them are available for Linux so hopefully you can find a suitable replacement. Other interesting Linux alternatives to SharpKeys are Kinto (Free, Open Source), xmodmap (Free, Open Source), xcape (Free, Open Source) and X Keyboard Extension (XKB) (Free, Open Source).
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.