I personally will not allow people in the EU to use any software I write going forward, I imagine other open source developers will take these steps as well.
That being said, if you don't audit your open source libraries, you should be held liable. I've seen open source encryption libraries do some really dumb things that I wouldn't touch with a ten foot pole. Yet they are some of the more popular ones.
This over the top article is, I guess, pointing to open source software that's used by an individual directly from the source as an enduser and then causes harm, not to parts of commercial software that includes open source software when they talk about holding open source devs liable.