Hi Damien
You can use just Event Tickets & Event Tickets Plus without using The Events Calendar (or Pro). The free plugins are required to run the paid plugins, but tickets can run separately from the calendar if you want.
The front end can be a different language. The translations of our plugins is a community project with more details at http://translations.theeventscalendar.com. We are limited in what languages we can support translating on our end, but several languages have a good deal of community contributions to make it 100% ready. It is worth noting that our most current versions of our plugins are not 100% compatible with WPML, but we hope to resolve that in the future.
Is there anything else I can help you with?
Thanks
Courtney