JBIG2 is a compression format for lossless and lossy encoding of scanned monochrome documents at moderately high resolution. It is very efficient in that domain, claiming 100:1 compression. jbig2dec is a decoder-only implementation of the format.
Open source project that offer summary and download services on this page is a project that carry out their development work on other open source development sites. Their work is linked to this page via a feature called OFI, and their work is not carried out here on OSDN site.