In reply to Hunky Dory:
If you can see what software the wiki is using you could then look up the documentation online. There might be a logo or some text somewhere saying what it is. MediaWiki, DokuWiki, PMWiki are popular wiki software.
However I suspect if a login/account creation is not obvious then it's likely to be set to private access only. They may have withdrawn open access if don't have someone to maintain the site. Without someone keeping an eye on it then it's likely to get bombarded with spam.