I use a private install of JIRA on my network, but also use the Sphider search engine to index everything. Unfortunately as has no understanding of authentication it cannot index JIRA issues unless the projects are marked as public.
This was originally a small script to generate pages for Sphider to index, with the resulting links redirecting 'real' users to the relevant page on JIRA. There's a lot more to it now, and the documentation needs to be updated, though the script will now allow you to create a static HTML mirror of some (or all) projects within your JIRA install, for use as a fallback or display on the net.
Most of the script should be self explanatory, but for some outdated documentation, see http://www.bentasker.co.uk/documentation/development-programming/273-allowing-your-internal-search-engine-to-index-jira-issues
You are welcome to raise issues within GitHub, however I track the project within JIRA itself. A static HTML mirror of the issue tracking can be viewed at http://projects.bentasker.co.uk/jira_projects/browse/JILS.html
Jira-Issue-Listing is Copyright (C) 2014 B Tasker. All Rights Reserved.
Released Under GNU GPL V2 License, see LICENSE.