Actually I have tried myself Autohotkey and Keyclone.

Keyclone costs 10$ and it is less then the time I spend on digging for info about AHK scripts costs

It is much easier to start with Keyclone, you just download it, pay for it and ready to go. Problem with Keyclone is that shift/crtl etc. modifiers are currently not working (or maybe only for me since people say it works) but it seems the creator is working on it

Autohotkey is free but takes some time to configure it. Also there is problem: I dont know how to determine main and clone windows for 5-box so you cant press for example one button and other clients recieve other keys. Otherwise there is sticky guide about Autohotkey.