When iPhoto for iOS first launched the foundation noted:
"The OSM data that Apple is using is rather old (start of April 2010) so don't expect to see your latest and greatest updates on there. It's also missing the necessary credit to OpenStreetMap's contributors; we look forward to working with Apple to get that on there."
In the end it turns out that an iOS developer may have helped get the credit added.
The OSM Foundation has made informal contact with staff at Apple and, in addition, one of our volunteer mappers who is an iOS developer spoke to people at Apple. We believe it was the latter that precipitated adding the attribution - it's great to have such an active and engaged community!
You can purchase iPhoto from the App Store for $4.99.