I am unsure whether your plugin is safe for Adsense.
Accoring to http://support.google.com/adsense/bin/answer.py?hl=en&answer=48182:
Sites showing Google ads should be easy for users to navigate. Sites may not change user preferences, redirect users to unwanted websites, initiate downloads, include malware or contain pop-ups or pop-unders that interfere with site navigation.
So, is the Facebook Page Promoter Lightbox AdSense safe?
I appreciate if you could answer this from your point of view/experience and perhaps give a link to Google answering it (if available).