HarfBuzz is distributed under the “Old MIT” license.

Permission is hereby granted, without written agreement and without license or
royalty fees, to use, copy, modify, and distribute this software and its
documentation for any purpose, provided that the copyright notices and the
following two paragraphs appear in all copies of this software.

In no event shall the copyright holder(s) be liable to any party for direct,
indirect, special, incidental, or consequential damages arising out of the use
of this software and its documentation, even if the copyright holder(s) have
been advised of the possibility of such damage.

The copyright holder(s) specifically disclaim any warranties, including, but
not limited to, the implied warranties of merchantability and fitness for a
particular purpose. The software provided hereunder is on an “as is” basis, and
the copyright holder(s) have no obligation to provide maintenance, support,
updates, enhancements, or modifications.

See https://github.com/harfbuzz/harfbuzz for the complete copyright-holder
list and per-file notices.
