From what I can see in their readme, this is basically a key remapping utility without any of the advanced macro functionality that Input Remapper has.
For example, I can create a macro in Input Remapper that is bound to the F12 key and will press keys 1, 2, and 3 in order at a certain rate and repeat for as long as I hold down that F12 key.
This utility would just allow me to remap a key to another without that repeat or timing functionality.