The Ahem font belongs to the public domain. In jurisdictions that do
not recognize public domain ownership of these files, the following
Creative Commons Zero declaration applies:

  The person who has associated a work with this document (the "Work")
  affirms that he or she (the "Affirmer") is the/an author or owner of
  the Work. The Work may be any work of authorship, including a
  database.

  The Affirmer hereby fully, permanently and irrevocably waives and
  relinquishes all of her or his copyright and related or neighboring
  legal rights in the Work available under any federal or state law,
  treaty or contract, including but not limited to moral rights,
  publicity and privacy rights, rights protecting against unfair
  competition and any rights protecting the extraction, dissemination
  and reuse of data, whether such rights are present or future, vested
  or contingent (the "Waiver"). The Affirmer makes the Waiver for the
  benefit of the public at large and to the detriment of the Affirmer's
  heirs or successors.

  The Affirmer understands and intends that the Waiver has the effect
  of eliminating and entirely removing from the Affirmer's control all
  the copyright and related or neighboring legal rights previously held
  by the Affirmer in the Work, to that extent making the Work freely
  available to the public for any and all uses and purposes without
  restriction of any kind, including commercial use and uses in media
  and formats or by methods that have not yet been invented or
  conceived. Should the Waiver for any reason be judged legally
  ineffective in any jurisdiction, the Affirmer hereby grants a free,
  full, permanent, irrevocable, nonexclusive and worldwide license for
  all her or his copyright and related or neighboring legal rights in
  the Work.

(reference https://web.archive.org/web/http://creativecommons.org/licenses/zero-waive/1.0/us/legalcode)