They can sue if they can prove that the code wasn’t reversed engineered in a clean room. Meaning nobody who wrote code looked at the original code. One person or group examines the software and writes the specifications and another group implements the specification without the teams interacting with each other. And usually a lawyer has to be involved and review the specification. The separation of teams is called the “Chinese Wall”
And depending on interpretation of the law if the people writing code used a decompiler that can be seen as breaching the “Chinese Wall” since the implementation is then not based solely on the specification but based on the original code.
They can sue if they can prove that the code wasn’t reversed engineered in a clean room. Meaning nobody who wrote code looked at the original code. One person or group examines the software and writes the specifications and another group implements the specification without the teams interacting with each other. And usually a lawyer has to be involved and review the specification. The separation of teams is called the “Chinese Wall”
And depending on interpretation of the law if the people writing code used a decompiler that can be seen as breaching the “Chinese Wall” since the implementation is then not based solely on the specification but based on the original code.