In the past, the Cheetah licence allowed installation on 2 computers, not used at the same time, as posted by Frank above. One example may be on your work desktop, and then also on your laptop so you can work out of hours / away from the office. So yes, using 1 licence on 2 machines at the same time is a violation of the EULA, but in my experience Martin is a reasonable chap to deal with. Unless he chooses to respond here it may be best to send him an email and discuss with him direct.
Your honesty in this matter is to be applauded. Well played sir.