I don't get the link, so yes, apparently one has to register. Personally I find that quite horrible. There are serious efforts underway to open up research, and putting stuff into yet another walled-garden (or rather, dozens of different walled-gardens) is a step backward.

Consider that the people that put their stuff their would ordinarily perhaps have put it on their personal homepage or some e-print service, so comparing it to the $20 fee of publishers is not the right comparison.