> Whether the makers of my software are responsible is a contractual matter - and nearly all open source licenses include a disclaimer of warranty and a limitation of liability, including the GPLv3 (see sections 15–17).

That was true in the US until MacPherson v. Buick in 01916 and in the UK until Donoghue v. Stevenson in 01932. Nearly all proprietary software licenses include the same disclaimer, but they are on slightly firmer ground in doing so, since typically those licenses are in fact contracts under common law, while the GPL explicitly purports not to be a contract and is very likely correct about that.

The kind of statutory imposition of liability we're discussing here would have to specifically outlaw such contract terms in order to work at all. You could imagine a statute that would specifically exempt open-source software licenses from that, but as explained comprehensively in this thread, such a statute would certainly not be the one that was passed.