This plugin moved to http://confluence.atlassian.com/display/JIRAEXT/Groovy+Runner. There is some background info here though.
I discovered the JIRA Groovy Runner recently, whilst looking for a starting point to integrate Jython in to JIRA. I succeeded in adding a Python runner, but then realised it wasn’t particularly useful, me not being a strong Python programmer.
However, it did make me look harder at the Groovy Runner, and manage to extend it somewhat to cover Conditions, Post-Functions, Validators and services… In theory you can cover all the areas where JIRA provides something to hook in to, eg Portlets, Reports, Listeners, Services etc.
