Author here. We chose to offer a dual commercial license for this case, which is not GPL and carries none of the obligations regarding sharing source code.
Of course the tradeoff is that it is not free (as in beer), but if your startup is getting sold then hopefully you got enough value out of our software to pay for a commercial license.
Of course the tradeoff is that it is not free (as in beer), but if your startup is getting sold then hopefully you got enough value out of our software to pay for a commercial license.