Multilanguage

Depends what you mean: the plugin admin area is currently only in english, but the link-parsing part should be language-independent in most cases, see for example the last two examples at https://onebox.surrealroad.com/wikipedia-link-examples/

I’ve see the code for the text domain but in the plugin there is not .op file for translate it.

you’re correct, I will add one for english.

Thanks i’ll translate in italian ??

Added to git master https://github.com/surrealroad/wp-onebox/blob/master/languages/onebox.pot