I can register it without any problems. I don't know what browser you are using. I have tested it on Chrome and Firefox and it works fine. You could send an email to support@saola.in and I could create a user for you.
I'll try my best to answer you.
1. I believe you can do it with a standard webserver setup. But when you want to share scripts and files to other users I believe it would just become a bit more cumbersome.
2. For me files within files is a lot more easier. It is not possible to add comments to directories. When you create a directory its just a string. It is not easy to add extra information to the directory itself. I may be wrong.
Again a webserver+CGI would definitely work no doubt. The app just simplifies it for you. Its the same thing with content management system. Its simpler to use them rather than build it manually. Also I plan to add the ability to share files.
Thanks for bring up Acme and Plan9. Having used Acme as a primary editor for a while I definitely plan to bring some of its features along. I have ported part of plumbing to elisp though very rudimentary. Though I wonder how plumbing could be implemented in the web. It is an interesting thought.
My first choice was Clojure, but eventually went down the JavaScript way. If there are more supporters for a lisp like language I will add support for it in the future.
Another here as well...I was excited up until I saw it wasn't self hosted, I had wrongly assumed it was aimed at running a personal/internal web server/site.