A Wiki Copycat is a wiki that begins by copying large portions of another wiki's content.
When someone covers much of the same topics as another wiki, it discourages collaboration and can negatively impact the wiki in which they copied.
While text on a wiki is usually available under a free license, which means anyone is welcome to reuse that content as long as they provide attribution back to the original creators and as long as both wikis use the same license, it is usually frowned upon in the wiki community to copy large quantities of text or create a mirror of existing wiki.
To see if a wiki is a potential Wiki Copycat, type "Special:Log" into their "Search" box and press "Go". If you see a large number of articles that were "imported", it may be they started out by copying information from another wiki. (You make have to change the pulldown under "Logs" to "Import Log" if the wiki has been around for awhile.)
If you are going to contribute to a wiki and edit their pages, think about finding the original source and doing your editing there. Don't support Wiki Copycats!
Also click on a few of the articles that were imported to see if they give proper attribution to the wiki from which it was imported. If not, they may be in violation of the Creative Commons Attribution-ShareAlike License which most wikis adhere too.
If someone is are not providing proper attribution for MagicPedia articles, please add them to the list of offending sites at: MagicPedia:Mirrors and forks