What will you do if your work is not paid, not 「devoted」, someone has derived it, and then, when you make derivation of the original code, they come back and want you to pay for it?

So here is a brief description of the whole affair.

A software, I denote 「A」 here, was developed and only a nominal payment was paid. Please note that I never signed a 「sell the ownership」 nor a 「devote this to someone else, or the open source community」 permission. The whole development was done on my own computer; hence I have full ownership of the software.

Someone (「B」 in later text) derived and sold the software without prior getting my permission, and I got to know the fact after a long while. From all aspects, this is illegal, however I did not complained anything when I found this. Ok they got what they want, fame, money, but after all, according to Chinese law, I still have the right to sue them and get what I am supposed to have.

I derived 「A」 some months ago for a certain government department and it is now running at their server. Unfortunately, B complains that it was derived from C. It is completely bullshit and drives me into angry.

DID YOU EVER THINK ABOUT ME WHEN YOU SOLD DERIVAL WORK OF MY SOFTWARE?

DID YOU EVER THINK ABOUT WHAT I FEEL WHEN I SAW MY SOFTWARE ILLEGALLY DERIVED AND BEING SOLD WHEN I GOT NOTHING?

DID YOU EVER THINK ABOUT WHAT I THOUGHT WHEN I WAS DEPRIVED WHAT I OUGHT TO HAVE AFTER HARD WORK?

I want to say, YOU SUCK, GO TO HELL!!! YOUR FOOLISHNESS IS THE ROOT CAUSE OF ALL MY SADNESS AND I WILL NEVER FORGIVE THIS!! YOU WILL FINALLY PAY BACK!