alt Hacker NewsFor the RuneScape wiki at least, they seem to have a paid agreement with jagex to maintain the wiki. Which makes a lot of sense, the game devs probably want to have a good wiki for their own game (especially for a game like RuneScape). Not sure if that's the case for the other wikis they host, though.
That is correct. However the jagex funding is not really enough[1] so they added ads. The League wiki seems to be also under this model, but I suppose they got a better deal. The Minecraft Wiki doesn't have any ads at all, and it's just been feeding off by the runescape wikis.
[1]: https://runescape.wiki/w/Forum:Funding_the_wikis