TitleInstaller can supposedly install anything you can get from the eShop.
However, with the paid stuff, you need to retrieve a certificate from Nintendo, which NUSGrabber and similar tools are incapable of retrieving (unless I'm missing something, or I'm thinking about the original Wii). Without this certificate, the program cannot be decrypted by the console, and will as such fail to install.
Game updates (and apparently free titles) don't have private certificates, and as such can just be installed directly.
So I'm sorry, but there is no piracy with this.
