I have decided to do something good for the community - I especially want to thank Gideon and Scott and early developer NoahY. From those guys I learnt a lot regarding q2a and PHP over the past years - so please see my free release as a contribution to you :)
Instead of charging for the On-Site-Notifications Plugin I release it for free.
Screenshot:

Description: Facebook-like / Stackoverflow-like notifications on your forum's website that can replace all email-notifications.
Video-URL: https://www.youtube.com/watch?v=C86rdJkGP3k&wide
"Your users complain because they get too many notification emails from your forum? You lose overview and you do not know anymore what new events are important for you? Then the On-Site-Notification-Plugin is the perfect solution for you."
more info at: https://github.com/q2apro/q2apro-on-site-notifications
Installation Note: If you are using the q2a history plugin, you should disable/remove it from your installation before installing this plugin. Otherwise events would be written twice to the database.