Why he is free...the real reason....

Swiss officials say that they are letting him go, because the U.S. hasn't given them several documents they asked for. The New York Times explains:

Ms. Widmer-Schlumpf said the American authorities had rejected a request by her ministry for records of a hearing by the prosecutor in the case, Roger Gunson, in January 2010 which should have established whether the judge who tried the case in 1977 had assured Mr. Polanski that time he spent in a psychiatric unit would constitute the whole of the period of imprisonment he would serve.

“If this were the case, Roman Polanski would actually have already served his sentence and therefore both the proceedings on which the U.S. extradition request is founded and the request itself would have no foundation,” the Swiss Justice Ministry said in a statement.