This was exactly what I was after to assist in envigorating a community so thank you for your efforts.
I'm running Buddypres 1.7.1, latest bbPress and Invite Anyone and now this plugin on my http://www.geekandjock.com site.
I've set up a half dozen initial achievements for first comment, first group join, 5 invites and register.
I can't seem to get the achievement to engage though. I can assign an award manually via the User Admin panel and the popup achievement works fine.
Is there something I'm missing that might prevent this working?