I’d like to use Skuid to replace some Formstack forms, build a wizard, put it on a Force.com site, embed it in an iframe on our Wordpress site. Will anyone be able to see it / use it if they don’t have a Skuid license? Or is there a Guest User license that covers that one page or something?
That would require one license.
Correct. See this tutorial: http://help.skuidify.com/m/11720/l/114236-build-force-com-sites-with-skuid