Comment 3 for bug 1640370

Quick answer: use it as you would any other font, ideally with a short message in the imprint conveying useful information to the reader and telling them where to also get it from if they like it: eg.

  "Code samples typeset in Ubuntu Mono Italic 14pt. The Ubuntu Font Family is available from http://font.ubuntu.com/ and licensed under the Ubuntu Font Licence 1.0 http://font.ubuntu.com/ufl/ "

or to use a real-world example found in the found of pretty much every O'Reilly book:

  "The cover image is from The Royal Natural History. The cover fonts are URW Typewriter and Guardian Sans. The text font is Adobe Minion Pro; the heading font is Adobe Myriad Condensed; and the code font is Dalton Maag’s Ubuntu Mono."

The intention behind libre/open licences is to give *additional rights* not normally available with most fonts: ie. allowing modification and sharing.