Mindtouch Auth SSO

Drupal 6: This module provides single-sign-on via a Drupal website, to a Mindtouch website which already uses Drupal as an Authentication Provider. Allow users to login to both Drupal and Mindtouch apps/sites at once with only one sign-on action (Drupal login), removing the ordinary need for users to sign in at each app/site separately.

Drupal 7: This module implements a remote authenctication provider which Mindtouch can connect to. Optionally, the Drupal 7 sub-module for single-sign-on (described above) can be enabled.

Mindtouch has a Drupal authentication provider built-in, which is capable of authenticating login credentials against a Drupal database for versions up to Drupal 6. The Mindtouch built-in Drupal authentication provider can't work with Drupal 7, for two reasons:
It doesn't know about D7's new password hash algorithm, and, even if it did, it couldn't properly salt the supplied password in order to match the Drupal database hash value.

Therefore, the Drupal 7 version of this module provides both a "remote" (rather than "local", or built-in) authentication provider which Mindtouch can use, as well as the single-sign-on feature (which is in an optional, included, separate sub-module).