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.
/e: let me clarify, I agree with the three comments under me. You, the commercial entity using my code, is accountable. I am not liable if you as a private person run my shitty code. I was thinking of private persons and being on the hook for my GitHub repos.
Basically they can't just brush off responsibility for using FOSS code by saying "well I didn't write it, it's not my fault" unless you as the FOSS developer are selling them a support contract for any potential issues in your code.