My mother uses some software to organize and add metadata about photos -- dates, people included, commentary, etc. She has probably thousands of photos that she has scanned and been archiving. Unfortunately, the program she has been using only exports this by creating an executable that can run on windows, which runs a viewer to see the data, and it stores all of its data in a proprietary, undocumented format. Since this is data that she wants to archive and distribute, this program is completely unacceptable.
I want to recommend to her a program to do this that is free/open source, uses an open and documented format, and preferably is cross platform. It also needs to handle various image types without converting to another format (including jpeg, tiff, etc). The data she is compiling will eventually be viewed on many platforms (Linux, Windows, Mac, maybe more), so the most critical thing is that the format be open.