A wikifarm is a site where you can set up your own wiki easily and for free. Examples include PBwiki.com, Welcome to Wikispaces and many others.
This may be desirable if you have content which is unsuitable for Appropedia, due to its content (e.g. political or strong point of view) or because you wish to use a different license (e.g. a non-commercial license). Be sure to check the conditions before you begin using it, e.g. whether you are able to choose you own license.