Yann Levreau built AlethZero as an early attempt at a Mist-style browser before Fabian Vogelsteller restarted that effort in JavaScript.
In Fabian Vogelsteller's Early Days of Ethereum interview, Bob Summerwill described AlethZero as "a really ugly programmer tool, kind of like a million controls", and Fabian agreed it was "that early Mist browser." The experience of AlethZero informed the decision to rebuild Mist as a JavaScript/Electron application.