WikkaWiki is an open source wiki application. Forked from WakkaWiki in 2004, WikkaWiki today powers hundreds of websites worldwide and is known for its lightweight engine.
WikkaWiki is a mature project aiming to remain faithful to WakkaWiki's heritage of a lightweight engine with readable and accessible code. Easy extensibility/hackability (without sacrificing performance) are among Wikka's most prominent and appreciated features.