Wikimedia (the parent of Wikipedia) pays most people at Wikimedia very generously. The issue is most people involved, outside of tech, contribute little or nothing to Wikipedia which is the reason people are donating.
If you're writing a program that relates to image (really, just JPEG and TIFF since they're all that support it) metadata, also check out IPTC which is more directly related to metadata that isn't about the image. Both EXIF and IPTC come from the TIFF standard.