can i join on tlauncher

No you can't. 

The SWDTeam does not support cracked clients and you will not be able to join DMU through clients such as Tlauncher. 

I think if you have any client running and try to join dmu, it will either ban u the second u join or simply not let you join. I could be mistaken

how do we join then

If you're using an illegal, cracked, "free" copy of the game then you do not join.

If you want to play on DMU then you need to buy a genuine copy of the game.