Is Reunion 9 compatible with Mountain Lion (Mac OS X 10.8)?

Yes, except for the installation issue noted below.

If you download a maintenance update of Reunion 9 or if you download and install Reunion 9 on a new Macintosh with Mountain Lion, Apple's new security feature called "Gatekeeper" will, by default, interfere with launching the Reunion 9 app. You can override this as follows.

  1. In the Finder, Control-click (or right click) the Reunion 9 app icon (either in the Dock or in the Applications folder).
  2. Select Open from the top of the pop-up menu that appears.
  3. Click Open in Gatekeeper's warning message (see image below). If prompted, enter an administrator name and password.