MyBB Community Forums

How could I translate a plugin when there is not any language pack to edit? I do not want to directly edit the plugin.
How colud I create a .lang.php file?

You'd have to modify the plugin I'm afraid. That's the only way if the plugin isn't using the language system.

Could you explain me how to do that?

Open the plugin file in a program such as notepad++, find the phrases you wish to translate and translate them.