My problem above is solved. I've found how the localisation system works for the plugin.
I've another issue :
On the front end, some strings appears to not being translated, even if they are in the translation files.
This code is the translation file language.php:
'YOUR_REGISTRATION_DATA_HAS_NOW_BEEN_SAVED_BUT_YOUR_a8bdff' => 'Vos données d\'inscription sont maintenant sauvegardées, mais votre souscription n\'est pas encore active. Vous devez maintenant payer votre souscription:',
This code is in the original file :
'YOUR_REGISTRATION_DATA_HAS_NOW_BEEN_SAVED_BUT_YOUR_a8bdff' => 'Your registration data has now been saved, but your subscription isn\'t active yet. You need now to pay the subscription:',
And there is this code in view.showparams.xml :
<param name="intro_text" type="htmlarea" height="170" cols="40" rows="5" default="Your registration data has now been saved, but your subscription isn't active yet. You need now to pay the subscription:"
How does this work ? Do you know how can I make the translation appears in the front end ?
Best regards
Paul