[thesethings]

It's not exactly what you're looking for, but there enough of an overlap for me to mention Review Board, written in Django, that is really for code review, but supports screenshots.

Anybody looking to make open source "visual feedback" software may want to check out the code.

http://www.review-board.org - Hope somebody posts to this thread with a previously unknown open source tool. Because the tools you listed (proofhq.com, getblackboard.com) look great!

[runningskull]

Hey, sorry for the late reply. Thanks for mentioning Review Board. I'm a big Django fan anyway, so at the very least it'll be insightful to review it.

Thanks. And I guess we're out of luck on an open-source Backboard clone...