I have several old Aperture libraries lying around in my hard disk, and also massive Lightroom catalog. Without the application they were created it can be a major pain to access the images. It’s worth mentioning that Apple has officially stopped development of Aperture, so in future the application will likely go away entirely.
Snapselect is a software that can access the images in those libraries. Currently it supports iPhoto, Aperture and Lightroom and fully supports RAW.
According to the creators, Snapselect can also find duplicates of the images.
I will check it out and write a review soon.