hex is a Haskell-based reimplementation of TeX. It currently only implements the macro functionality and very basic typesetting with DVI output. Its goal is to implement all of TeX and have a PDF output option.
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.