NEW YORK -- Danny Goldberg, a longtime music industry executive, took over as chief executive of Air America Radio on Thursday in the latest sign that the liberal talk radio network is gaining its footing after a rocky start. Goldberg, whose New York-based record label Artemis represents artists including Steve Earle and the late Warren Zevon, took over from acting CEO Doug Kreeger, who stepped aside in December but remains an advisor and board member for the company.