Super Dimension Fortress (SDF, also known as freeshell.org) is a non-profit public access UNIX shell provider on the Internet. It has been in continual operation since 1987 as a non-profit social club. The name is derived from the Japanese anime series The Super Dimension Fortress Macross; the original SDF server was a Bulletin board system created by Ted Uhlemann for fellow Japanese anime fans. From its BBS roots, which have been well documented as part of the BBS: The Documentary project, SDF has grown into a feature-rich provider serving members around the world. Services SDF provides free Unix shell access, web hosting and many other features at the user membership level. Additional programs, capabilities and resources are available at "patron" and "sustaining" level memberships, which are granted with one-time or recurring dues in support of the SDF system. The SDF network of systems that serves its membership currently includes NetBSD servers for regular use (running on DEC Alpha- and AMD Opteron-powered hardware) as well as retrocomputing environments: a TWENEX system running the Panda Distribution TOPS-20 MONITOR 7.1 on two XKL TOAD-2 computers, a Symbolics Genera system, and an ITS system Free Membership Services SDF provides free Unix shell access and web hosting to its users. In addition, SDF provides increasingly rare services such as dial-up internet access, and Gopher hosting. SDF is one of very few organizations in the world still actively promoting the gopher protocol, an alternate protocol that existed at the introduction of the modern World Wide Web. The system contains thousands of programs and utilities, including a command-line BBS called BBOARD, a chat program called COMMODE, email programs, webmail, social networking programs, developer tools and games. Most of the applications hosted at SDF are accessed via the command-line, and SDF provides K-12 and college classrooms the free use of computing resources for Unix education. SDF also supports multiple retrocomputing experiences, including free user accounts on TOPS-20 and Symbolics Genera operating systems that are running live and accessible via the internet. Dues-paying membership services There are additional services that are made available on SDF systems to users who apply to be "patrons" and pay one-time dues of US$36 for "Lifetime Membership", and still more services available for at US$9/quarter "sustaining membership", including services such as NextCloud, and access to a large disc-array server. At the sustaining membership level, members are authorized to validate new users to SDF's free