Notice he called it "graal the adventure" and not "graal classic". The whole "wtf 2 classics" argument isn't really valid in this scenario other than that they use a similar tileset and combat. Knowing Stefan though, chances are he's just gonna ask to take parts of your server and throw them onto Classic iPhone.
Anyways, Graal classic puts more emphasis on social content, customization, and simple stuff whereas Graal the Adventure would have far more complex quests and story.