This wiki (www.freenethelp.org) allows new articles to be posted under 3 licenses:
Under the Public Domain (PD), under the GNU Free Documentation License (GFDL) and under the Creatives Commons (attribution) (CC).
By default, all text falls under the PD, unless explicitly stated otherwise.
When editing, all editors agree their modifications fall (also) under the PD. When modifying text of an article under another license then the PD, their text also falls under the (rules of the) respective Licenses. Thus, modifications made on this wiki of a non-PD licensed article, automatically are dual-licensed (PD and the respective license).