Information disclosure on 3rd party?

[dapphp]

What is the name of your state?
California

I hope this is in the right category, but it seemed the closest to me. I received a letter from a lawyer threatening to sue me, however, they gave me 6 actions I could take in order to avoid further actions. One of them I think may not be lawful or legal, so I'm sure an expert here can answer that.
They demanded this of me: "(5) supply all identifying information (name, address, e-mail, IP, etc.) for anyone making NeoPets-related programs (this is how you were identified) or selling Neopoints;"

Shortly thereafter, they stated the following, "We will require you to actually supply information responsive to (5) as we will not accept a statement that you do not posess such information."

Can a private company actually force me to disclose information on other civilians? I see it as a grounds for someone I may implicate to sue me for giving away private information. And if someone turned me in respondant to their demands (as they state) am I able to fight them somehow for that?

Thank you very much for reading...

To read about my situation further, or if you have experience with intellectual property matters, please see my first thread located [URL=http://forum.freeadvice.com/showthread.php?t=241167]here[/URL]