I just installed it on the 3yo's computer because he always wants to play Vanguard with mommy and Brandon (which he can't do).
FreeRealms is aimed for the 6-10yo age range from what I can tell. It is very very basic, and as long as you can read, that's the requirement. I don't even think someone older than 10 would really be that interested in the game.
I wouldn't even call it an MMORPG. It was very theme park and linear but that may be because of the tutorial. You basically just chase a kid to a farm to scare away "robgoblins" who are stealing corn. Then when you get there the farmer casts an illusion on you to turn you into a big scary troll looking thing, and you run through the farm and all the "robgoblins" get !!! above their heads and run away and you succeed.
Thats about as far as I got. I mean, if the farmer can put an illusion on you, why can't he put one on himself and scare the "robgoblins" away? Anybody with a brain wouldn't play the game.
But then again, alot of people liked the new Star Trek where Kirk takes the disrupter out of the romulan's holster when he was trying to throw Kirk over the cliff (instead of just shooting kirk with his disrupter)... So maybe there is an audience for this type of game...