Generally open source software is free, which is a very attractive feature, to be sure. But since wiki content is often controlled by open source licenses, the ownership of any wiki content is not entirely clear. Wiki content being created in a collaborative effort by multiple authors is the norm, so the authors may be considered to have a joint copyright interest in the content they create.
Most everyone on the Internet reads Wikipedia, whether they rely on it or not, but few understand how wikis work or who owns the content. Understanding content ownership is important, because so many people freely contribute to wikis. If the owner of the wiki decides to revise or move the content, that could lead to a lawsuit.
Similarly, if the contributors move the content, that too could lead to a lawsuit. A case was recently filed on just this issue — moving content. However, it is not copyright infringement that’s alleged, but rather trademark infringement and unfair business practices.