From the SecondLife main blog:
Posted by Joe Linden on Sep 7, 2010 11:04:13 AM
As of 10am PT Wednesday, September 8, the Emerald Viewer will be blocked from logging in to Second Life as a result of violations of our Policy on Third Party Viewers. Residents who have been using any version of the Emerald Viewer will need to use a different Viewer to access Second Life. You can download the official Second Life Viewer, developed by Linden Lab, here. Or you can learn more about alternative Viewers, developed by third parties, here. There are several new Viewers listed in the TPV Directory, so there are many alternatives available to you.
We take Residents’ privacy, safety, and security very seriously and will take action to enforce the policies that help protect it. As our CEO, Philip Rosedale, has blogged about, we recently removed the Emerald Viewer from our Third-Party Viewer Directory due to violations of our Policy on Third-Party Viewers.
Since then, we have been in communication with the Emerald development team and have requested several changes in order to remedy violations of our policy, including changes necessary to meet our privacy requirements, and to address GPL license violations. Unfortunately, the team was unable to comply within a stipulated time frame. As a result, we have decided to block logins from the Emerald Viewer in order to protect our Residents. All versions of the Emerald Viewer will be blocked from logging in to Second Life as of tomorrow at 10am. Please be aware that attempting to circumvent our blocking to access Second Life with a banned Viewer is a violation of the Policy on Third-Party Viewers and may result in the loss of one's account.
At the same time, they updated the Approved Third Party Viewer list, and included Phoenix.