http://www.roblox.com/Coming-Soon-GTA-ROBLOX-Pre-Order-place?id=176851014
You are probably wondering, if the game is going to be free, why do I need to pre-order? Well here is your answer... it will give limited edition content such as a special weapon when you join.
So what makes this GTA different from the rest?
It contains contact missions like GTA: Online! You teleport from the server into others to complete fun missions. Want to pre-order? You can buy it now from the link above!