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.
Note 2021-07-19: ttf2pt1 has not been maintained since 2003, and it is getting increasingly difficult to make it compile without significant warnings on modern compilers, which in turn is making it difficult to maintain this package on CRAN. It is possible that in the future, I will not have time to keep this package on CRAN.
If you are interested in maintaining this package, please file an issue on the repository.
This product includes software developed by the TTF2PT1 Project and its contributors.