XWiki is a Java open source wiki under a LGPL license. In addition to being a full-featured wiki, it is also a second generation wiki allowing small collaborative web applications to be written easily and quickly. XWiki has a vibrant community of developers and users, massively expanding during the last year. The community is made of individual users as well as companies around the world which are using XWiki for Intranets and Communities.
One example of an important project built on top of XWiki is Curriki (http://www.curriki.org) which is open source itself and hosted inside XWiki's source repository. Curriki is an online service for creating and sharing open education resources (based on XWiki and the Google Web Toolkit). Note that we plan to also select projects directly related to the work in progress on Curriki.