I think AKASHA uses the default ipfs config, and stores the ipfs data at ~/.ipfs. However, it comes with its own ipfs executable, so people who haven't installed ipfs can use it too. But if your normal ipfs daemon is running, you have to shut it down first, and then launch AKASHA. I already wrote to them that they should either find a way to "hop onto" an already running daemon, or implement a built-in node just for AKASHA. At any rate, it should be built-in, not as an external ipfs-connector.
I think the content is stored on the IPFS, and it's validated by (and paid for on) the blockchain.