It's not exactly copylefting - the T&Cs still won't let you modify the content or redistribute it further - but yes, you are allowed to republish the article body (although it's hard to do so at the moment due to the omission of paragraph breaks, which we're working to fix).
If you just show our headlines, you won't be asked to display our ads. If you opt to publish our article bodies we reserve the right to ask you to include our ads some time in the future.
What about the 24 hours rule? I don't see the point of publishing news for 24 hours - links to the article on our site after we remove it won't work, for example. Are we supposed to query your API each day for each article or something like that?
If you just show our headlines, you won't be asked to display our ads. If you opt to publish our article bodies we reserve the right to ask you to include our ads some time in the future.