In Google webmaster Tools there is a "Structured Data Testing Tool", which, although the purpose of it is for rich snippets and microdata, it looks like it can be used to see if Google recognizes the url with the ADDTHIS snippet as still being valid with authorship linked to a Google Plus account.
I pasted your extended url with snippets into the test window, clicked Preview, and it seems to show up fine in their test results.
This may indicate that as as long as Google recognizes the url as being connected to authorship with a Google Plus account, then they would not penalize it because of the added AddThis snippet. Also, AddThis has a 100 domain authority in open site explorer, and there is a tracking link in the script to their site.
<script type="<a class="attribute-value">text/javascript</a>" src="//s7.addthis.com/js/300/addthis_widget.js#pubid=ra-52b47a3152487f9b">script>
I would guess that there is a possibility that if Google's algorhithm recognized their domain as a trusted domain with strong authority, then that would also be helpful to avoid any SEO penalties. (Open Site Explorer shows addthis.com having a 100 domain authority!).
