Yes, ubercart.org is still currently running a on a D5 installation. Everyone had been so busy with the 2.x push, well, no one really had time to do much else. So, now's a great time, during a minor lull before the D7 port, or 3.x release, to upgrade the website. After a false start last year trying to move ubercart.org to d6, we're ready to try again.
So, without further ado, www.ubercart.org.php5-4.dfw1-2.websitetestlink.com is ready for testing. Please browse around a bit to make sure there are no major issues before we roll over. It is a copy, so the latest posts to ubercart.org may not be there. We are looking to test functionality, not content.
You can report any issues back here, at ubercart.org (not www.ubercart.org.php5-4.dfw1-2.websitetestlink.com) in this forum thread: http://www.ubercart.org/forum/ubercartorg/14899/ubercart_org_d6_attempt_2
Thank you for testing it out and providing your valuable feedback.