gPhoto is a program and library framework that lets users download pictures from their digital cameras. The libgphoto2 library gives you access to hundreds of models of digital cameras on several platforms. GIT repo and Issue tracker lives at https://github.com/gphoto/ these days.
Read, write and edit metadata
Perl library and command-line application for reading, writing and editing meta information (EXIF, IPTC, XMP, and more) in a wide variety of file formats (JPEG, TIFF, PNG, PDF, RAW, and more).