You just need to get your account on the approved list. Then you can edit. The only real requirement is that you're not a spammer and you obey the rules. What's your username?
The problem is partially due to spammers. I know ways to stop the spammers so we don't have to do that, but I don't have server access to implement those changes (among other changes) and the person who does hasn't responded to my emails about the issue. Maybe it's because I changed emails a long time ago and I'm going in her spam folder or something. The former person who had access was quite responsive. Maybe I'll petition for server access myself and see if they trust me. That's probably the right thing to do.
IMSLP is a great site, by the way. I'm honored that you would check out HymnWiki. :)
I'm actually planning to create some new wiki software customized for HymnWiki's needs, and finding a new server (or getting server access to the current one). Fortunately I have the sheet music I've uploaded on my computer already. So, I don't have to download all that. But the rest of the stuff will take time. MediaWiki isn't bad, though, but things could be simpler for people who've never used a wiki, and manipulating the database and categories could be more flexible. Plus, it would be nice to get rid of all those spammer accounts that already exist without deleting them one-by-one (hopefully that's already possible with server access, but I'm not aware of how).
There are specific things to be entered into articles, like names, dates, sheet music and licenses. So, I was thinking more like a data entry form instead of what we have now: a big page where you edit the whole thing with markup (or its headings). Then the order, styles, and such could be standardized and non-standard articles just couldn't be made without doing it on purpose. The forms should be rather flexible to provide for anything needed. Batch options for administrators should be easy with what I intend. Renaming articles and categories wouldn't cause issues with articles that link to them, either. I'm also wanting parent categories to inherit everything their children have, instead of having to go into the child category to see what's there every time.
Right now, I'm programming some database stuff which the wiki software and other things are planned to use.
I've established contact with someone with server access. Ideally they'll fix everything soon. If not, I'm requesting server access. If they don't grant it, then we'll have to wait until I get a server. That will probably be within a few months.
Okay, I got a reply recently about the issues specifically. My supervisor said she would address the issues as soon as she can. I might add that she must be pretty busy, though, as she supervises other sites (at least one is quite large). So, I don't know how long this will take. Hopefully soon.