As far as I can see is that TFWIki.net has the CC-BY-SA 3.0-Licence.
- Share — copy and redistribute the material in any medium or format
- Adapt — remix, transform, and build upon the material for any purpose, even commercially.
but (and that is the point)
the user didn't mentioned that the original text is from the TFWIki.net and his authors. If you want to copy & paste stuff from the wiki you have to make sure that you mentioning that you are not the author of this text.
And that count for Wikia as well because Wikia is under CC-BY-SA 2.0. Everybody can copy your text from the Wiki but has to make sure he is writing soem credits.
Plagiatism comes only if you have a strict copyright law when the authors don't want to publish his text in another fandom or wiki or article but you are still doing it.