Comic Sans is freeware: http://en.wikipedia.org/wiki/Core_fonts_for_the_Web

Installation is trivial (apt-get install ttf-mscorefonts-installer). I think it is a default package.

I don't think he needs to pay any license to use Comic Sans:

http://en.wikipedia.org/wiki/Core_fonts_for_the_Web

I've attended to a course on presenting in a French university. The professor actually recommended Comic Sans as the most suitable font. With a straight face.