Here's an epic TL;DR of everything that has happened at the Corcoran leading up to today, the day gallery admission became permanently free:
The Corcoran announced it would enter a partnership with the National Gallery of Art and George Washington University, which made a lot of people angry and sad, especially a group of former students, staff and supporters called Save the Corcoran. The Corcoran, GW and the National Gallery had to go to court to get approval to amend the museum's charter. But when they did, Save the Corcoran filed suit to block the action. They put up a good fight, but on Monday, the courts announced that the merger would go through.
So yep, now that the Corcoran is a part of the National Gallery, it will no longer charge admission fees. New hours of operation are Wednesday through Sunday from 10 a.m. to 5 p.m.