And this could be bad news for Open Source.
From TFA:
(If you're wondering where open source code fits into this planned approach to liability, the strategy has this to say: "Responsibility must be placed on the stakeholders most capable of taking action to prevent bad outcomes, not on the end-users that often bear the consequences of insecure software nor on the open-source developer of a component that is integrated into a commercial product.")
That answers your question "You pick up some package for nowt off NPM, who is the responsible person?". You are, at least in the first instance. If the package is deliberate malware then the author, and any third party who planted it in the repository, would also be responsible. If a particular repository were to become conspicuous for hosting malware then its operators might also become responsible; it would certainly encourage them to be able to demonstrate that they were making serious efforts to curate the contents.
My take on this is that it gives those who use FOSS in commercial products an incentive to take a more active interest in what it is they're using, review it, fix problems and send the fixes upstream.