We are still actively working on the spam issue.
SDF (full name: The SDF Public Access UNIX System) is a service that is marketed as a UNIX-based social network. In reality it is a UNIX shell account that has a number of features. Founded in 1987 as The Super Dimension Fortress Macross, an Anime-centric BBS, it has evolved. Very popular among Cyberpunk communities (like lainchan), it has a good series of people logging in daily.
To "validate" your account, you need to send by mail $1 to their HQ in Seattle, WA. This is to prevent spam and help with server costs. For another USD, you can get DF stickers.
To log in, you ssh into your account and then have access to the SDF's TTY.
Basic account features
The SDF server also hosts internet services for subscription rates. These include Dial-Up, DSL, and an ISDN connection.