It doesn’t matter if the employee acted in good faith. The former employer can still lawyer up and create a problem. And there is a reasonable probability that no one with executive authority signed off on the code repository simply because of the way software development happens and the standards In industry.

To put it another way, the legality matters less than the relationship. A lawyer can communicate with the former employer in a way that mitigates potential problems. Or say it is unlikely to be a problem.