How useful is xshellz? it is not allowed to use sudo nor to put graphic interface much less programs. So, what are you running this for? Could at least put a graphical interface but do not! And on top of that they block all the doors! What good is that then?
Be reasonable. Nobody provides a whole remote computer with full access to play with to random people on the Internet for a free sign up. However, as a regular user on a remote box, you can use the server's resources, run its already installed programs, store stuff in your home directory, write and run scripts, compile this and that locally, and so on.