After running the install wizard I can answer my first question: the default forum URL is /jforum/. I've changed the context to "Fora", so for me the URL is /Fora/.
However, this doesn't work without a source hack. The file /Fora/index.htm points to the servlet /Fora/forums/list.page, which causes WebRequestContext.parseFriendlyURL() to be called. That method expects its requestUri input parameter to be of the form /<module>/<action>.page, but, it's receiving "/Fora"/<module>/<action>.page, that is, the context name "/Fora" is prepended, causing UrlPatternCollection.findPattern() to fail, which in turn causes JForum.service() to forward to the 404 error page. I can hack parseFriendlyURL() easily enough to remove the offending "/Fora". But, can anyone tell me why it's there in the first place? Presumably I've set a configuration option incorrectly somewhere - can you point me to it?
Thanks!