Hmm GPL states any distributed modifications must be shared. So the employee does not violate any licenses by snagging a copy of the code that was distributed. I’m sure there may be other violations that may cause an involuntary termination event, but per the license the world now has the right (and the company is violating the GPL by not offering the code)

I will add if the company fixes their GPL violation then the employee is now violating the new license (since the GpL licensed code wasn’t valid in the first place). So it is best to not pirate any code even if you think it should be open (until the employer has confirmed in some way)