most fonts are very much not free, but in a “rights” sense rather than in a “standards” sense. since fonts are works of art rather than technical designs, open source licenses don’t really apply. when printing a book you typically select a font and buy a license for that font that only allows you to use it, not modify it.
in fact, most of the web is built with proprietary fonts that keep being used in spite of their licenses because the alternative would break everything.








i’d say using proprietary fonts is okay. the format itself is open, paying artists is always good, and there are some gorgeous fonts out there.