Hi Jean-Philippe,
For accounting you have at least two alternatives.
If you already have an accounting software, (shameless plug here) we developped a module to export accounting data from Dolibarr which is available at Dolistore.
If you want to do most of your accounting tasks into Dolibarr, the upcoming release, which should be released shortly, will have such a module as an experimental feature.
Keep in mind, however, that French tax regulations are very picky about the software you use and, unfortunately, free software won't be accredited anytime soon. Using free software for this particular task is still a big leap of faith.
Best regards,