Like LHC & Predicor@home, Einstein@home runs only under BOINC.
This means currently if non-windows, you've only got a cli.
If windows, you choose if run the cli or gui, and if gui if you wants to display the screensaver or not.
In both instances the actual crunching is done by the same application, so if you're not running the screensaver or have the gui stuck on the disk-tab there isn't any difference between gui & cli.
Well, if NT, you can install the cli as service.
The separate gui isn't currently finished, but the windows-version is nearly finished.