First and foremost thank you for your review and rating.
The plugin is free, there is no commercial version of the ShareThisBar plugin.
You misunderstood something, the ShareThisBar plugin has a Google +1 button integrated already and it's working. You can activate the Google +1 button easily. The Google +1 button is connected to individual articles or content on your web site.
But You are probably referring to the Google + badge, which is connected to your personal Google+ profile or Google+ page. The Google+ badge can be easily included into the ShareThisBar, because there is room for adding up to three custom buttons, simply by including code for your Google + badge into the appropriate ShareThisBar parameter. But I would recommend you to make custom Joomla module and to include code for Google+ badge, Facebook page,... and other "Follow me" badges into it.
Kind regards from Dusanka.