I downloaded the source package and dug through a bunch of the source java. I figured out the problem is there is no properties file. When I drop the JSPWiki.war into my webapps folder, and it gets unpacked by Tomcat there is NO /ini/jspwiki.properties created (which was what was trying to be read at the time of the NPE). If I was supposed to create that file manually, I didn't see that requirement in the quick start steps. I didn't dig into the war to see if the properties file was there and Tomcat was at fault for not unpacking it, or if it's not in the war at all. In either case, the properties file is obviously mandatory. Install.jsp needs to handle the situation of a missing properties file a little more gracefully than an NPE.
I'll go with the benefit of the doubt and say that maybe I have a unique situation and everybody else gets the property file created just fine. But I don't think so. I just upgraded to Tomcat 7.0.50. I downloaded the war, and crashed on the first page. Even if I have some unique situation that is causing this, an NPE on the very first page, and having to dig through the source code to figure it out is not a fun way to start using a new product. Did I miss a step along the way to get this installed and running? Thanks. Jerry