Z:gnu-www-ja-license-list--1150c5-Section 9.4 of the CeCILL comm/en

Section 9.4 of the CeCILL commits the program's developers to certain forms of cooperation with the users, if someone attacks the program with a patent. You might look at that as a problem for the developer; however, if you are sure you would want to cooperate with the users in those ways anyway, then it isn't a problem for you.