Johannes website is in English
https://johanneskok.com/index.php/en/i-telex
He also has a terminal program that runs off the RS-232 on the "special board"
https://johanneskok.com/index.php/en/i-telex-usb-terminal

There are also a site concerning using a Raspberry Pi
https://github.com/fablab-wue/piTelex

There is also a standalone windows program
https://github.com/detlefgerhardt/WinTlx

I'm sure there are others. this is what I've seen so far.
You can install google chrome and use the page translate feature in chrome other browsers might offer that too.