I mean, anyone can be sued for anything. I can file a lawsuit with basically zero legitimacy to it. It'll probably get thrown out, but you were still sued.

If the question is could someone win, potentially. The argument would basically have to be that the removal of that open source project is akin to other cases of negligent interference.

If this is a specific concern, consult a lawyer - 'cause I'm not one.

Doubtful. If linkedin had completely taken down their site, or put it all behind a login account, them this case would not have turned out the same.

Maybe if leftpad somehow tried to block only some users from using their publically available plugin.