CangrejoMail it's a mod of the popular webmail "SquirrelMail". All the html code has been changed to XHTML, this way, all the interface is handle by CSS with the possibility to work with themes.
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.