Well if for what ever reason the provided "guest" account doesn't work you can try to set up another account.

According to the [?]TPP wiki[?] you can do that for the DOS/Windows based tutorial like this:

Setting up an account

The TPP GUI comes with one user account. This account has ‘guest’ as both the user name and password. Below are instructions for making another account from a Cygwin shell. The Cygwin Bash Shell can be found under Cygwin in the Windows start menu.

Open the DOS shell by selecting Run under the Start menue and typing cmd. In the shell type:

cd c:\Inetpub\tpp-bin\users\

mkdir tutorial

cd tutorial

crypt isbTPPspc TPP > .password

and

chmod -R 777 C:\Inetpub\tpp-bin\users\tutorial

You have just created the password ‘TPP’ for the user ‘tutorial.’ In order to add a different username, create a tpp-bin/users/NEWUSER/ directory and run crypt isbTPPspc NEWPASSWORD > .password from this directory. In these examples "isbTPPspc" is the crypt key. This can be changed.

That is for Windows/DOS. Not sure something equivalent can be done under Linux. But since they use a Bash shell under DOS it might. You probably have to read the man pages with the distribution to find out how exactly.