Thanks for your suggestions and feedback on this issue.
This issue is now closed and will be marked as obsolete, as we have integrated a native invitation functionality within Confluence as of 4.2.5. For more information, please see the release notes: Confluence 4.2.5 Release Notes.
Whilst we have now implemented invites, we understand that there are a few capabilities that the original plugin had, that is not currently available with the new feature in Confluence. Separate issues have been created for them, feel free to vote for them there: