The Rttf2pt1 R package was created and maintained by Winston Chang on github for more than 13 years with a first commit on github the 11th of june 2012. The previous commit history of the package can be found here. The responsibilities and attention of Winston Chang are on things quite far away from extrafont and Rttf2pt1 these days. As a consequence he asked for another person to maintain the Rttf2pt1 package and I (Frederic Bertrand) volunteered (read here).
The following text is an update the original README.md from Winston Chang repository on github.
The Rttf2p1 package for R is meant to be used with the extrafont package.
This package contains the utility program ttf2pt1, and
is in its own package for licensing reasons. It will be compiled on
installation, so you need a build environment on your system.
This product includes software developed by the TTF2PT1 Project and its contributors.