You are only able to run one of them at a time. You can install and use the same license key on many machines but you can't run them at the same time as they will crash if I remember correctly. Also your license will be flagged for being used on multiple machines at the same time and could be banned. So as FrenchGuy said 1 computer = 1 license
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what if I stop using software on one computer and start on another? is it acceptable?
Sure. You can do that without any problem.
Best of luck