Born-again conservative David Zucker’s “An American Carol,” a spoof of “A Christmas Carol” with Uncle Sam straightening out a “Michael Moore type” on the 4th of July, is so good that it’s not going to be screened in advance for critics. Meanwhile, the real Michael Moore is giving away his new movie, “The Great Slacker Uprising,” free on the Internet. New is a relative term here; this self-promoting documentary on Moore’s ’84 college tour, which failed to topple Dubya, was originally commissioned by his former patrons the Weinstein Brothers as a DVD extra for a planned special edition of “Fahrenheit 9/11.” I caught a shorter version called “Captain Mike Across America” at the ’06 Toronto Film Festival before the Weinsteins gave him back the movie. And the price the would-be demagogue is charging may still be too high.