I'm not sure if she still is, but for a number of years, she was bound by an agreement with the Office of Independent Counsel that forbade her from writing a book.
She has appeared on at least one television special for which she was compensated, FWIW. I was watching the View (don't ask) a couple of months ago and Barbara Walters was talking about it. Walters likes Lewinsky, for some reason - perhaps on mistress to another.
Wow! I didn't know that. I hope she was VERY well compensated for entering into that agreement, but I can't see how the Office of Independent Counsel could legally compensate her for something like that, nor do I see how they could force it on her without compensation. I'd love to know more about this if you can point me to any informative source(s).