It depends, if you use IdleBuster just to make yourself active and still do the work, this is not cheating. You are still delivering results, you just want to free yourself from the micromanagement. But if you use IdleBuster without doing the work and delivering results, that is cheating and that is bad.
Use IdleBuster responsibly. Use it to circumvent time doctor or other time trackers which are super strict that you just don’t move your mouse for few seconds, it already recorded you as idle.
No need to keep moving your mouse manually, let IdleBuster automate things for you.