I'm happy to see this short story posted here, it is one that I deeply loved when I was 14 or alike, and read it again multiple times. But I wonder: how did it survive in those sites without being shut down by the Asimov writings copyright holders? Given that the story is short and highly shared, it was just tolerated?

EDIT: actually I see that the link historically posted here more often is now dead: multivax.com/last_question.html