The Suffusion Custom Post Types plugin is meant to help users transition out of Suffusion. If you have defined post types and taxonomies in Suffusion and are moving to another theme, this plugin will show you all the post types you have registered with the theme.
In addition, this plugin is necessary if you are using a version of Suffusion that is 4.0.0 or higher, because the Custom Types functionality of Suffusion is retired with effect from version 4.0.0.
For older versions of Suffusion this plugin is only required if you intend to move from Suffusion and are concerned you will lose your post types.
Support for the plugin can be obtained via the Support Forum.