I went through the article instructions and found that they may be out of date. I am brand new, so I am posting a very similar solution that worked for me after reviewing a MySQL startup script. I am running a personal license of Atlassian Confluence which uses Tomcat.
1. StartupItems.plist should be renamed to StartupParameters.plist
2. StartupParameters.plist should make use of an XML schema rather than the YAML version posted (am I correct in my assumption?)
My StartupParameters.plist file:
4. Test using /sbin/SystemStarter start Confluence. I noticed that Console still outputs the "unknown service" message, but it appears that it can be safely ignored in my case.
5. Make use of the same Tomcat script with the correct Tomcat startup.sh path.
6. Restart your system, and you should be able to access your Tomcat servlet location. In my case, it was the default http://localhost:8080/