Good question... Although everything appoints that J-11B is unlicensed copy of Su-27, it is interesting that Rosoboronexport did not made any official state on this, as well as Chinese official representatives in Russia and members of Commission for Science, Technology and Industry for National Defense did not want to talk with press about it.
In 1992. China purchased Su-27 and became first country, except former Soviet states, with this type in its arsenal. In 1996 Sukhoi and chinese SAC entered a contract according to which China supposed to built 200 examples from russian kits. After 95 finished J-11, China canceled the contract. Sukhoi proposed the modernized Su-27SKM, but China did not accept in favor of indigenous J-11B. Now, in this case indigenous means that J-11B is built on copied airframe of Su-27, but equipped with chinese avionics, technology and weapons. The both aircrafts look almost the same, and there are also naval J-15 and multi-role J-16.