The founder of a wiki site is the person (or people) who originally started it. Founders are distinct from leaders, although sometimes the two are the same person(s). In the case of Ward's Wiki (the original wiki), Ward Cunningham is both the founder and one of the leaders of creating content. In 2000, SunirShah forked some of the content to create MeatBallWiki which had few real leaders. Another example of a founder/leader is ClericofMadness, who created the Creepypasta Wiki. Wikipedia was co-founded by Larry Sanger and Jimmy Wales in 2001, but neither is very active today – Sanger left shortly after creating Wikipedia, and subsequently founded Citizendium in 2006; and Wales has mostly focused on outreach efforts, and subsequently co-founded Wikia with Angela Beesley.
Here on WikiIndex, we can highlight the founder of a wiki by adding the |founder = field (and their name!) in the wiki infobox; or, alternatively, we can provide more detail (outside of the infobox), including the date of foundation by using template:Founded by.