Flattr support on OGA was removed when we updated to Drupal 7 a year or two ago, because at the time the Drupal 7 Flattr module wasn't ready to go.  As it stand, Drupal 7's Flattr module is still in alpha, and hasn't been updated since July, so I didn't feel particularly good about including it here.  In any case, I've tried to put together a simple custom Flattr implementation for OGA.

If you're an artist and would like Flattr links to appear on your art, edit your user profile by clicking your username in the upper right and then clicking the Edit tab.  Scroll to the bottom and fill in your Flattr UserID, then save your profile.  From there on, Flattr links should appear on any art that you submitted and you are the author of.

Important note:  This is a brand new feature, and it hasn't been widely tested, so at the moment consider it to be in beta.  That is, while I'm pretty sure it'll work okay, I can't absolutely guarantee it, so please let me know if you run into any bugs.

Important note #2:  If you had flattr enabled back on OGA 1.0, you'll need to re-enter your flattr username in your profile.

Thanks!

Bart