SafeChat
They would use some of the really good add-ons (i.e kaje's vehicles) and sell them as "content packs" or "premium content"
Building wouldn't exist, well, sorta. You would only be able to place groups of bricks at a time, like a house, or a street, or a chair or something.
There would be freemason iconography blatantly posted all over.
You can't run people over.
No more weapons.
No tools.
No forums.
No spraypaint.
Can't paint people.
Hats and clothes cost money, real or in-game
In-game currency
Membership subscriptions
Official Master servers
Servers renamed "Worlds"
Or most likely they would abandon it all-together.