Forumatic has shut down its services on December 20th, 2016.
The phpBB open source project is going strong, so you can continue to use the same underlying software to power your forum. You will, however, need a new hosting company to provide you with server space to run the forum. Together with the phpBB project we recommend Bluehost, who we believe provide reliable and extremely affordable web hosting that supports phpBB. You may, of course, use another webhost of your choice.
Thank you for your support over the years.
Learn about Bluehost
Great phpBB Forum Hosting