This extension has the potential to be a great Joomla extension for ticket processing and sales once it reaches maturity. I hope that the developers keep working on it and integrate a payment gateway like paypal.
I recommend you don't pay for this extension until it has a viable payment option, because it is not very useful without one. The Seminar extension basically does the same thing as the current iteration of this extension and that extension is free to use.
PayPal has been adeed :) Backend is completely English and multilanguage. So I guess you have your Joomla! settings wrong. But thanks for your feedback