I would add that is not only code contributor did not write. It might be that contributor does not understand his legal obligations to his current employer and

I would add that is not only code contributor did not write. It might be that contributor does not understand his legal obligations to his current employer and I think probably no one is going to attach note from their company that they are allowed to contribute to the project. In the end paw shop is responsible if they are buying stolen goods, signing a paper is not a "get out of the jail free card" because a thief would sign on anything anyway just to sell stuff. Even if you get the paper that contribution is legal there is still a chance of legal trouble.