According to an article in the New York Times, Forbidden Broadway is taking a break in January with no immediate plans to start back up again.
"'When I look at the seasons coming up, I don’t particularly think we’ll have a great opportunity to have really funny numbers about "Shrek" or another "Guys and Dolls" revival or some of the stuff that’s coming out,' [creator Gerard] Alessandrini said by phone . . .'When Broadway becomes too theme-park-like, it makes it difficult, and it just looks like it’s becoming overly commercial the next couple of years,' he said. . . .
"Mr. Alessandrini said that 'Forbidden Broadway' might return to New York one day, but that, if so, it would be with a new format. 'We may think about doing "Forbidden Broadway: in the future, but not on an open-ended basis, but with one edition at a time,' he said."
I also looked at http://www.forbiddenbroadway.com/, but most of the pages return "not found on this server" errors.