Quoting Justin B Rye <jbr@edlug.org.uk>:
No, "patent liability" isn't about who owns the IP, it's about whether you're vulnerable to being sued for infringing it. Compare: http://ilt.eff.org/index.php/Trademark:_Liability
I finally found the correct expression in French: "responsabilité civile de brevet". It is what they are using in official law texts about intelectual property:
http://www.legifrance.gouv.fr/affichCode.do?idSectionTA=LEGISCTA000006179063&cidTexte=LEGITEXT000006069414&dateTexte=20110823#LEGIARTI000006279560