You only have until this message self destructs. You have to if you want to succeed. Don't worry, the answer isn't so you won't have to move much. There are coming to attack. Prepare the ship. You must defend yourself. Please try So you can survive.
Um... is a rebus something different in English than it is in Dutch? Because in Dutch, rebuses are made up out of pictures and added or removed letters (like a picture of a door with under it 'o = e'), and these things are called 'Droedels'.
They are using the positioning of letters to picture phrases. It's a bit hard to do with this text system, though. And I don't think this is the correct term. But oh well, I like it much more than actual rebuses.