[Deleted b/c it was inappropriate]
The wiki engine was called Radeox and rendered wiki markup into HTML. It was written in Java and open sourced from an existing Wiki application called SnipSnap [0]. If you have worked at Atlassian as a developer, you should have seen that name. It was also used as an example by Grails developers, e.G. in "The definitive guide to Grails"
References to it can be e.G. found here:
https://docs.atlassian.com/ConfluenceServer/javadoc/7.12.2/c...
The way macros are done and I have invented can e.G. be found here:
https://support.atlassian.com/confluence-cloud/docs/insert-t...
I have discussed things with Mike Cannon-Brookes long before you've joined the company. Sadly the oldest mail I can still find from Mike to me is from 2006 and was not about this topic.