The situation is complex, partly because Usenet was started in the USA before it signed up to the Berne convention. Therefore custom & practise on Usenet generally ignores the legal situation and unless someone does something really stupid the law pretty much ignores us.
Technically someone can create a Usenet post and restrict how it should be reproduced elsewhere. When GG first started many posters explicitly refused it permission to republish their posts. Google ignored them.
If Google ignored the legal situation and got away with it I don't think you will have any problems either.