Ukelele is a Mac OS X app that allows users to create customized keyboard layouts and Unicode keyboards. With Ukelele, users can create different layouts for different languages, or create their own unique layouts. The app also includes a library of existing keyboard layouts, so users can quickly find what they need. Ukelele also supports Unicode input and offers a range of tools for creating, modifying, and testing keyboard layouts. The app also allows users to export their layout to a file in order to share it with others.
It modifies the keyboard, but it is absolutely not an alternative to the full functionality of Ukelele. They are just two completely different programs in the same area ...