But the C library WiringPi is deprecated. Pi4J is just an interface for Wiring Pi.
So the dev-team of Pi4J need to find another C code core.
$ gpio -v
gpio version: 2.50
$ cd /tmp
$ wget https://project-downloads.drogon.net/wiringpi-latest.deb
$ sudo dpkg -i wiringpi-latest.deb
$ gpio -v
gpio version: 2.52
The development team should write a tutorial how to contribute and help with the Pi4J project.
Many users don't know how to join the development team because they don't know here to start in the code or don't know how the project is organized.