You still can’t get new HBO shows, like this season’s “Game of Thrones,” without paying for TV. But starting in May, you’ll be able to get some of the premium cable channel’s older stuff online — via an Amazon Prime subscription. That means Amazon Prime subscribers will be able to see shows that have already run on HBO, like The Sopranos and The Wire. And they can also watch older seasons of some shows that are still on the air, like Girls, three years after they air. It’s the first time HBO has offered access to its catalog via a streaming video service that’s not its own HBO Go. And it gives Amazon an important bragging right/differentiation point as it tries to gain ground on rival Netflix. A person familiar with the deal says HBO did not shop the catalog to Netflix or other potential Amazon rivals. Unlike HBO subscribers who use HBO Go, Amazon customers won’t be able to get all of HBO’s library.