>They should be liable if they go out of their way to write harmful information/software,
In the interests of free speech I staunchly disagree.
If someone writes a virus, that should not be a crime. If someone uses that virus to cause harm or damage, that should be a crime.
But if they are FOSS developers, there is no contract, because there is no exchange. In this case, developers should have about as much responsibility as say authors who write books for the public. They should be liable if they go out of their way to write harmful information/software, but if they took reasonable precautions, they should be fine.