If you want to run JIRA as a server on OSX, you will need to configure it to load as a userdaemon. OSX has migrated configuration scripts from services such as cron, rc, or init.d to the launchd utility. There are some good introductory and in-depth explanations of it's function on the web. You can find out more about launchd here:
It's easier to use Lingon (http://lingon.sourceforge.net/) to define your plist xml definitions for import into launchd; although because launchd does not permit forking of processes you will need to call $TOMCAT_HOME/bin/catalina.sh directly.
I'd advise adding the <UserName> tag to tell OSX which user to run Tomcat under, eg running Tomcat under root is not recommended. JAVA_HOME will be inherited as an environment variable for whichever user you define in the XML definition - so configure it for that user's .profile in their home directory.
If you wanted to run JIRA as a WAR web-archive, and use OSX's factory install of Tomcat, please see the JIRA WAR installation instructions.