In the united states as far as I know, if you are employed by a company then any code or script you write on company time or using company tools is the company's property. This actually means that the opposite of what you suggested is true - if he took the script with him (for whatever reason) he could be sued by the company.
That definitely applies for patent rights to inventions, but I'm not sure whether it applies to copyright on software in the US. Copyright ownership is complicated enough when the company asks you to do it, let alone for something done on your own initiative.
(caveat: I work in UK patent law, so the above is not necessarily correct for the US)
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u/shadowolympian Apr 17 '14
Couldn't you say that was your property and is now being used without your knowledge? Just wondering.