What it is

It watches the typed keys and displays them on the screen in a nice way. Latest update supports mouse as well and displays button presses next to the cursor

How can I use it

You need QT creator to recompile or just download the latest release from the "Releases" section on Github

You need to make your user part of the "input" group like this:

sudo usermod -a -G input $USER

Without this step your user will be unable to open the input device and you will need to run this program as root (not advised).

How it looks like

Here is the program with mouse support

Here is the old demo of the program in action (no mouse support version):

Can I use it commercially ?

Yes, it's MIT licensed