[Edit] "Engine" is ambigous, wiki render engine would be more precise [0]. To be transparent and because it is not and was not my intention to mislead people: the code was a library that rendered Wiki markup into HTML and had a plugin/extension system to e.G. render syntax highlighted code, diagrams and integrate with third party systems. It implemented this with a macro system using {...} syntax. You would need to add at least load/safe e.G. with Hibernate to have a (minimal) Wiki application. But with Radeox you could create your Wiki app in perhaps 100 LOC.
[0] https://www.researchgate.net/publication/200773455_The_Radeo...