Yes, this plugin has been retired. It’s a shame because it worked really well but the company cannot keep up with such a high demand:
Unfortunately, because of the demanding needs of the plugin (to update conversations in a timely fashion) and limited resources we won’t be able to support it any longer.
There are two alternatives/fixes to it:
1) Use Disqus (powered by BackType)
2) Update the plugin to reflect the new BackType API
Official blog article (and steps to fix the plugin): https://blog.backtype.com/2010/10/retiring-the-backtype-connect-wordpress-plugin/