It looks like they've been around since 2010, which surprises me because GitHub was around for a year or two before that iirc. I still envy that username, though!
Sometimes people assume the low character count usernames are taken and don't even try. I've snagged some cool twitter accounts this way (not low though but like regular words).
I always loved downloading them DRM-free. Because it felt like I had actually owned it instead of just reading it from some website that could snatch it back at any second. I know Library Genesis is still up and running fine, but this is a warning of things that could happen.